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Instrument Information

INSTRUMENT_ID IRIS
INSTRUMENT_NAME IRIS
INFRARED INTERFEROMETER SPECTROMETER
INFRARED INTERFEROMETER SPECTROMETER AND RADIOMETER
INSTRUMENT_TYPE CCD/SPECTROGRAPH
Infrared Spectrometer
INSTRUMENT_HOST_ID AAO
MR9
VG1
VG2
INSTRUMENT_DESC
 
Instrument Overview
===================
  INSTRUMENT: INFRARED INTERFEROMETER SPECTROMETER
    INSTRUMENT: INFRARED INTERFEROMETER SPECTROMETER AND RADIOMETER
 
  SPACECRAFT: MARINER 9
          HOST: VOYAGER 1
          HOST: VOYAGER 2
 
IRIS is a camera and low-resolution spectrograph for the wavelength
 
range 1.0-2.5 microns.  It was designed and constructed at AAO.  The
  Instrument Information
    Instrument Information
detector is a 128x128 pixel format mercury-cadmium telluride (HgCdTe)
  ======================
    ======================
NICMOS2 array with 60 micron pixels. The detector is housed in a large
    Instrument Id                  : IRIS
      Instrument Id                  : IRIS
dewar and operated at a constant temperature between 80 and 82 K.  It
    Instrument Host Id             : MR9
      Instrument Host Id             : VG1
      Instrument Host Id             : VG2
is cooled using a closed-cycle compressed helium pump.
 
    PI Pds User Id                 : BJCONRATH
      Instrument Name                : INFRARED INTERFEROMETER
    Instrument Name                : INFRARED INTERFEROMETER
                                        SPECTROMETER AND RADIOMETER
IRIS mounts at the Cassegrain focus and can be fed either at f/15 or
                                     SPECTROMETER
      Instrument Type                : INFRARED INTERFEROMETER
with the f/36 chopping secondary.  Swapping between these two f/ratios
 
requires a top-end change.  The chopping secondary is not
    Instrument Type                : INFRARED INTERFEROMETER
 
    Instrument Mass                : 22.3
driven, and is merely used to provide a convenient f/ratio.
 
    Instrument Description
    Instrument Serial Number       : IRIS M
    ======================
The following options are available:
    Instrument Manufacturer Name   : TEXAS INSTRUMENTS
 
      The Voyager IRIS instrument consists of a Michelson
 
f/15 imaging, 1.94 arcsec pixels
      interferometer for measurements in the thermal infrared and a
  Instrument Description
f/15 imaging, 0.61 arcsec pixels
      single channel radiometer that operates in the visible and near
  ======================
f/15 grism long-slit spectroscopy, H window, resolution 300
      infrared.  The two components of the instrument share a 50 cm
    The Mariner 9 Infrared Interferometer Spectrometer (IRIS)
      Cassegrain telescope with an effective focal length of 303.5
f/15 grism long-slit spectroscopy, 2.0-2.4 microns, resolution 300
 
    instrument is a Michelson interferometer with a circular
      cm.  The angular field of view is 0.25 degree.  Light passing
f/36 imaging, 0.79 arcsec pixels
    aperture 4.3 cm in diameter.  The field of view is also
      through the telescope is divided into two beams by a dichroic
f/36 imaging, 0.27 arcsec pixels
      mirror, with that longer than about 2.5 micrometers going to
    circular, with an angular diameter of approximately 4.4 degrees.
f/36 echelle spectroscopy, 0.9-1.5 microns, resolution 400
      the infrared interferometer and radiation between 0.33 and 2
    The effective spectral range of the interferometer is 200-2000
f/36 echelle spectroscopy, 1.4-2.5 microns, resolution 400
      micrometers going to the radiometer.  The effective spectral
    cm**-1, and the apodized spectral resolution is 2.4 cm**-1.  The
    dwell time for each interferogram is 18.2 s.  An
      range of the interferometer is 180-2500 cm**-1 (4-55
f/36 grism long-slit spectroscopy, 1.2-2.1 microns, resolution 100
 
      micrometers) and the apodized spectral resolution is 4.3
    image-motion-compensating mirror, inclined at an angle of 45
The following filters are currently provided:
    degrees to the axis of rotation, is part of the instrument;
      cm**-1.  The beam splitter of the interferometer consists of a
 
      multilayer dielectric coating applied to a cesium iodide
    however, it was never used for motion compensation.  The beam
Standard broad band J, H, K (1.25, 1.65, 2.2 microns)
    splitter of the interferometer consists of a multilayer
      substrate.  The moving mirror is mounted on one end of a motor
Broad-band K' (1.9-2.3 microns)
      shaft; the moving mirror of an auxiliary reference
    dielectric coating applied to a CsI substrate.  The moving
Narrower Kn filter (2.0-2.3 microns)
    mirror mounted on one end of a motor shaft is driven at a
      interferometer is attached to the other end of the shaft.  A
1bandpass 1.08 (He I)
    constant velocity of 0.0235 cm/s during the recording of an
      0.5852 micrometer neon line source is used for the reference
1bandpass 1.64 ([Fe II], Galaxy)
      interferometer; the signal from this unit is used by a phase
    interferogram.  The fringe-control/reference interferometer uses
1bandpass 1.65 ([Fe II], at 0.0020 S(1))
      speed and to quantize the analog signal from the main IR
    different optical path than the IR signal, making use of the
1bandpass 2.16 (Brackett gamma)
      detector.  The latter is a low impedance, Schwartz-type
    center of the beamsplitter.  The center of the beamsplitter is
1bandpass 2.25 (H2 2->1 S(1))
      thermopile with a noise equivalent power (NEP) of about 2E-10
    coated to perform well in the visible and near-infrared for the
      Watt/Hz**1/2.
4bandpass 2.21 (continuum)
    reference interferometer.  A 0.6929 micrometer neon line source
 
4bandpass 2.34 (CO/continuum)
    is used for the reference interferometer with a photomultiplier
 
    detector.  The signal from this unit, along with a velocity
      The spectral response of the radiometer, which is designed to
    transducer, provides feedback control of the main
The K' filter was defined by Wainscoat & Cowie (1992 Astron J. 103,
      measure the broadband reflected solar radiation, is controlled
      by the dichroic mirror and an additional coating on the
    interferometer, and as an initiator for the analog to digital
332).  The sky background is lowered by a factor of about 3 and the star
      radiometer side of the mirror.  The radiometer detector is an
    conversion process.  Synchronization of the data stream with the
signal is typically 92% that at K.  The Kn filter has almost as high
    spacecraft clock is accomplished by a phased locked loop which
      eighteen-junction thermopile with an NEP of 4E-10 Watt/Hz**1/2.
sensitivity, and greatly reduces the effect of water vapour at the short
    slaves the mirror motion to the highly stable clock frequency.
      A sapphire window is placed in front of the detector to reject
end of the K' filter. There is some fringing with the [Fe II] filters,
but it appears to cancel when the sky is removed.
      unwanted long-wave radiation that may result from temperature
    The main IR detector is a thermister bolometer operating at 250
 
      gradients within the instrument.  The signal from the
    K with a bias voltage of 500 V.  The entrance window of the
      radiometer detector is fed to a low noise, low-drift dc
    instrument is also CsI to permit operation to 200 cm**-1.  The
There is no shutter in IRIS.  For the full array the minimum exposure
      amplifier with a time constant of approximately 2.7 seconds,
    window seals the interferometer from moisture and dust, and it
is 1.5 seconds.  In summer broad-band K is saturated at f/15 wide, and
    supports an optical filter designed to reflect sunlight and
      and then to three different output circuits.  The first circuit
at all times of year there is a risk that dome flats cannot be taken in
    thermal radiation below 2500 cm**-1.  The filter also protected
this configuration.  Standard stars are observed in a smaller window
      integrates the radiometer signal over the 45.6 seconds it takes
which can be read in 0.22 seconds.
    the CsI window from atmospheric degradation during storage and
      to record an interferogram, thus providing the average of the
 
      reflected sunlight during the time the infrared spectrum is
    launch.  Calibration is provided by alternatively viewing deep
      recorded.  The second and third circuits provide the analog
    space and a built-in blackbody maintained at a temperature of
The readout proceeds row by row up the array.  An integration starts
    296.4 K (see instrument calibration description) by rotation of
      signal from the radiometer as well as the signal amplified by a
the moment the relevant pixel has been read, so that the first rows are
    the image motion compensation mirror.  The dynamic range of the
exposed earlier than the last rows.  The readout noise is about 120
      factor of 8.  These latter channels are sampled every 6 seconds
      and digitized.  The timing of the samples, and their
electrons in the most time-efficient mode, and 40 electrons in the
    instrument is 8000:1 with an NER (noise equivalent radiance) of
alternative.
    0.5 x 10**-7 W cm**-2 sr**-1/cm**-1.
      relationship to events in a single-frame read out of an image
 
      are given in Table 1.
 
Scientific Objectives
    The temperature of the instrument is passively and actively
=====================
                     Table 1. IRIS and ISS Events
    controlled to operate at a nominal temperature of 250.0 +/- 0.2
 
    K.  One surface of the instrument is not covered by thermal
            Event                         ISS line count
    insulation; it acts as a passive radiator to deep space.  Active
Being a general user instrument IRIS was developed to be an extremely
            ____________________________  ___________________
    thermal control is maintained by the action of thermostatically
versatile camera/spectrograph combination to be useful for a wide range
            ISS frame start               0 (0 seconds)
    controlled heaters.  The thermostat kept the IRIS optical module
of astronomical observations.  It has both wide and intermediate field
            IRIS frame start              167
    temperature constant to within +/- 0.2 K from the time of the
optics, providing a total of four separate imaging scales, and can
            IRIS interferogram start      179
switch in a matter of seconds between slit spectroscopy and imaging
    initial cooldown prior to launch, through the transit phase, and
    during orbital operation at Mars [HANEL_ETAL_1972A,
            IRIS radiometer samples       217,317,...,717,
with a choice of two image scales. In the wide field mode it is used as
    HANEL_ETAL_1972B, HANEL_ETAL_1972C].
                                          and 017, 117 of
a survey instrument and to map extended objects such as the central
 
                                          the following frame
region of our galaxy, star-formation regions and nearby galaxies.  The
 
            IRIS pointing information #1  350
smaller image scales are used for detailed work including mapping
  Scientific Objectives
            IRIS interferogram peak       375 +/- 5
planetary surfaces and atmospheres, studies of the nuclei of galaxies,
  =====================
            IRIS pointing information #2  750
and supernovae observations.  The spectroscopic capability allows
            ISS shutter close             767
    The scientific objectives of the Mariner 9 Infrared
determination of redshifts, remote sensing of planetary atmospheres and
compositional studies of stars and galaxies.
            ISS frame end                 800(48 seconds)
    Interferometer Spectrometer (IRIS) investigation include the
 
    following:
 
Calibration
===========
    (1) Determination of the carbon dioxide pressure at the surface.
      In order to visualize the effects of quantization uncertainties
 
      directly, it is sometimes useful to convert the radiometer
    (2) Determination of the vertical temperature profile of the
        atmosphere.
      watts at the detector back into data numbers (DN).  The
Several methods have been used in an attempt to calibrate the SL9 data.
      relationships are:
These are: photometric standard stars, polar haze, and Jovian
    (3) Determination of the total amount of atmospheric water
 
        vapor.
satellites.  The photometric standard stars were used to calibrate the
            For Voyager 1:
    (4) Identification and determination of the abundances of other
imaging data, and the polar haze and satellites were used to calibrate
 
the spectral mapping data.
        minor atmospheric constituents.
 
               Sampled data (normal gain):
    (5) Determination of surface temperatures.
Detectors
                  DNn = (WADn * 1e+08 - 2.51937) / 3.39426
    (6) Determination of chemical or mineralogical composition and
=========
               Sampled data (high gain):
        information of the physical structure of the surface layer,
 
        including polar deposits.
                  DNh = (WADh * 1e+09 - 1.55472) / 4.26206
 
               Integrated data:
The detector is a hybrid array of 128x128 pixel format with 60 micron
                  DNi = WADi / 1.42145 * 1e+09
    These objectives are accomplished through the analysis of
pixels.  The IR-sensitive material, mercury-cadmium telluride (HgCdTe),
 
    measurements of thermal emission spectra.
is bonded to a silicon multiplexer by individual indium columns.  The
 
            For Voyager 2:
array was manufactured by the Rockwell International Science Center of
 
Thousand Oaks, California, and it would be appreciated if this fact
  Calibration
               Sampled data (normal gain):
were mentioned in all publications based on IRIS data.
 
  ===========
                  DNn = (WADn * 1e+08 - 6.33020) / 3.40070
               Sampled data (high gain):
    Calibration spectra were periodically recorded while observing
Filters are used to limit the wavelength sensitivity of the detector to
                  DNh = (WADh * 1e+09 + 6.57589) / 4.24459
    either deep space or an on-board warm blackbody (T = 296.4 K).
radiation longward of 0.8 microns (otherwise the silicon multiplexer
               Integrated data:
    One pair of calibration spectra is generated for every 14
will continue to detect bright objects throughout the visible range).
                  DNi = WADi / 1.42047 * 1e+09
    spectra of Mars (7 spectra of Mars, on-board black-body, 7
The detector is tuned to cut-off at 2.5 microns on the longward end.
 
    spectra of Mars, deep space, etc.).  Scaling of the raw Martian
 
    spectra to the calibration spectra specifies the Martian spectra
The hybrid nature of the chip ensures that the idiosyncracies of each
part are compounded.  The detector displays the following
    in absolute radiometric units.  The calibration procedure for
      Pairs of baseline levels are averaged at the beginning and at
characteristics:
    the Mariner 9 spectra is similar to that previously described
      the end of the 45.6 second integrations, occasionally resulting
 
    for Nimbus 4, see HANEL_ETAL_1972D.  The excellent thermal
      in half-integral DN values for the integrated radiometer data.
 
    stability of the Mariner 9 IRIS permitted the entire ensemble of
i)    A bias level that differs for the three readout methods and totally
      dominates most data.
      Despite the stability of the calibration data (see below), a
    1766 calibration pairs acquired during the Mariner mission to be
    averaged to provide a single set of calibration parameters.
      small systematic error may remain.  Comparison of spatially
ii)   A dark current caused by the chip and by stray radiation inside the
      resolved IRIS observations of Jupiter and Saturn shows that
    Consequently, the random error introduced into the individual
      IRIS dewar, which therefore depends on the dewar configuration.
    target spectra from calibration is extremely small.
      reflectivities derived from Voyager 1 and Voyager 2 IRIS
iii)  Wavelength-dependent fixed pattern noise, both coarse (ripples across
 
      instruments are in the ratio 0.883:1.  An investigation was
      the chip with a typical wavelength of 40 pixels) and fine (at short
      wavelength, individual hotter and cooler pixels).
      made of albedos of various objects (Jupiter, Io, Ganymede,
    The calibration is carried out independently for each wavenumber
    interval by using the equation I = B(Tw) * (C1 - C2) / A1 / (C3
      Callisto, and Saturn), as determined using the two instruments.
iv)   Dead and permanently bright pixels (failures in the indium columns
      etc).
      When compared to groundbased determinations, no systematic
    - C2), where C1 = the instantaneous spectral amplitude for Mars,
    C2 = the average of the spectral amplitudes for the cold
      differences were apparent for either instrument, within the
v)    Vertical striping caused by the architecture of the silicon
      multiplexer.
    calibration source (deep space), and C3 = the average of the
      uncertainties.  Thus, a systematic error on the order of 10%
      may exist in the calibration of one or both of the IRIS
    spectral amplitudes for the warm calibration source (on-board
vi)   Sectors of circular arcs with a common centre off the chip to lower
      instruments' radiometer systems.
    reference blackbody).  B(Tw) is the Planck function for the
      right, attributed to growth effects in the doped silicon; known to
 
      the cognoscenti as the silicon swirl.
    temperature of the warm reference blackbody (Tw).  Tw is an
      The temperature of the instrument is passively and actively
    average of eight transducer measurements made immediately before
vii)  Bright or dark splotches about 3 pixels across and <1 amplitude in
      flat-fielded data.
      controlled to operate at 200 +/- 0.5 K with a maximum drift of
    and after each interferogram.  A1 is the reciprocal value of the
      +/- 0.1 K/day.  A thermal radiator mounted on the
    emissivity of the black paint used in the warm calibration
viii) Nonlinearities that become particularly serious around 60000 ADU, or
      20000-30000 above bias.
    source, an aluminum plate with 30 degree V-shaped grooves
      interferometer cools the instrument by radiating to deep space.
 
      Three sets of proportionally controlled heaters provide fine
    painted with 3M 401-C10 Black Velvet paint.  While this paint is
    relatively black over most of the instrument spectral range,
      thermal control for the primary telescope mirror, secondary
The procedures for removing all these effects are now standard, though
    small glass beads contained in it give rise to emittance
      mirror, and the interferometer.  It is necessary to maintain
there still seem to be occasions when not everything is cleaned out
    variations of a few percent near 480 cm**-1 and 1100 cm**-1
      temperature differences between the three components to less
adequately. Dark and/or bias subtraction is used to remove (i) and (ii),
    which are characteristic wave numbers of silicon dioxide.  The
      than 0.1 K.  In addition, high-powered 'flash-off' heaters are
after which (viii) is removed by a simple linearity correction as used
      available for increasing the instrument temperature by
    correction factor was derived from laboratory reflectance
in optical CCDs, while (iii), (v) and (vi) flat field out using a
      approximately 70 K.  These are controlled by command.  These
    measurements on a duplicate blackbody, from similar measurements
wavelength-matched observation of a continuum source.  The bad pixels
    on the same type of paint, kindly made available by James
[(iv)] can only be tolerated and replaced by interpolation with the
      have been used to warm the instrument during cruise periods to
      reverse a gradual change in the elastic properties of a
    Aronson (private communication), and finally from comparisons of
surrounding pixels, as necessary.  The detector originally displayed 70
      silicone compound in the Michelson motor dampers and
    the warm and cold calibrations of the interferometer while in
bad pixels, but this number has steadily been increasing with the age of
the detector.
      beam-splitter mounts.
    orbit around Mars.  All three methods were in agreement;
 
    consequently, the emissivity correction of the warm calibration
 
    source has been applied to all spectra.  The emissivity of the
A very bright star that saturates the detector does not bleed along rows
    Science Objectives
    reference 'blackbody' is listed below:
or columns; the excess electrons recombine harmlessly.  However, you may
 
    ==================
see a slight brightening along rows that pass through it.  Similar
    Wave                          Wave
      The scientific objectives of the Voyager Infrared
streaks passing through saturated bad pixels are seen on dark frames.
 
    Number         Emissivity     Number         Emissivity
      Interferometer Spectrometer (IRIS) investigation include the
      following:
    (cm**-1)       (cm**-1)
The remnance is acceptably good.  Highly oversaturated images fade from
 
    370            1.00           1000           0.98
significance in a minute or two.  There is a long tail to the remnance,
    375            1.00           1005           0.98
     (1)  Identification and determination of the abundances of
however, so that long dark exposures taken even half an hour later can
show a weak afterimage.
          gaseous atmospheric constituents;
    380            1.00           1010           0.97
 
    385            1.00           1015           0.97
     (2)  Determination of the helium abundance of the
Electronics
          atmospheres of the giant planets;
    390            1.00           1020           0.96
===========
    395            0.99           1025           0.96
     (3)  Determination of the energy balances of the giant
 
    400            0.99           1030           0.96
          planets through measurements of their total thermal
          emissions and Bond albedos;
    405            0.99           1035           0.95
The chip is slow to read out.  To read and reset every pixel requires
    410            0.99           1040           0.95
     (4)  Determination of the three dimensional thermal
nearly 1.5 sec; to read and not reset requires 0.9.  The readout
    415            0.99           1045           0.94
          structure of the atmospheres of the giant planets and
proceeds row by row up the array.  An integration starts the moment the
          Titan;
    420            0.98           1050           0.94
relevant pixel has been read, so that the first rows are exposed
    425            0.98           1055           0.94
     (5)  Inference of information on atmospheric dynamics;
earlier than the last rows. There are 9.5 electrons per ADU.
 
    430            0.98           1060           0.94
     (6)  Inference of the infrared optical properties of
          clouds and hazes;
    435            0.97           1065           0.93
There are three ways of reading out the array, and they have different
    440            0.97           1070           0.93
     (7)  Determination of the temperature, composition, and
uses.  Method 1 was used for the SL9 data.  In method 1 the incoming
    445            0.96           1075           0.93
          structure of the surfaces of satellites without
charge accumulates for the exposure time, after which it is read and
          atmospheres;
    450            0.96           1080           0.92
each well is reset to the bias level.  This is the end read, Er.
    455            0.95           1085           0.92
     (8)  Determination of the thermal characteristics of
Method 1 is normally suggested for broad-band imaging, or situations in
          Saturn's rings.
    460            0.95           1090           0.92
which the expected count rate is high, because the readout noise for
 
    465            0.95           1095           0.92
this mode is high (~120 e-).  However, it is the most efficient readout
 
    470            0.95           1100           0.91
      These objectives are accomplished through the analysis of
because there is scarcely any dead time between reading a pixel and
    475            0.95           1105           0.91
      measurements of thermal emission spectra and broad band
      These objectives are accomplished through the analysis of
readying it to accept more photons (there are other dead times in the
      reflected solar energy.
    480            0.96           1110           0.91
      measurements of thermal emission spectra and broad band
system, at the start and end of exposures when processing and writing
 
to disk occur).
      reflected solar energy.
    485            0.97           1115           0.92
 
    490            0.98           1120           0.92
 
    Operational Considerations
    495            0.99           1125           0.92
Once read out from the detector, IRIS data are stored temporarily in
    ==========================
    Operational Considerations
    500            0.99           1130           0.93
the external memory (XMEM) unit, where they may be manipulated before
    ==========================
    505            0.99           1135           0.94
      The IRIS instruments on Voyager 1 and 2 operated normally
finally being sent to disk.  Normal processing takes the form of
    510            1.00           1140           0.95
      The IRIS instruments on Voyager 1 and 2 operated normally
coadding various cycles of an observation and median filtering to
      throughout the mission.  The infrared interferometers of both
    515            1.00           1145           0.96
remove cosmic rays and other transient events present on only one
      instruments experienced a temporal decrease in responsivity,
      throughout the mission.  The infrared interferometers of both
    520            1.00           1150           0.96
      instruments experienced a temporal decrease in responsivity,
      believed to be due to a gradual stiffening in silicon compounds
exposure.  For the SL9 data no such intermediate processing or coadding
    .              .              1155           0.97
was performed.  Instead, in drift-scanning mode successive exposures
      believed to be due to a gradual stiffening in silicon compounds
      used in the mirror mounts and motor dampers.  However, this was
    .              .              1160           0.98
      partially reversed by using the flash off heaters to raise the
were stacked in the XMEM as a cube as the telescope was scanned, and
      used in the mirror mounts and motor dampers.  However, this was
the entire cube was dumped at the end of the scan.
    .              .              1165           0.98
      temperature of the instrument periodically during cruise
      partially reversed by using the flash off heaters to raise the
 
      between encounters.
    945            1.00           1170           0.98
      temperature of the instrument periodically during cruise
 
Location
      between encounters.
    950            1.00           1175           0.99
 
========
    955            1.00           1180           0.99
 
    Calibration Description
    960            0.99           1185           0.99
    =======================
    Calibration Description
    965            0.99           1190           0.99
        Latitude:   031o 16' 37.344''S       (31.27704 degrees S)
    =======================
    970            0.99           1195           0.99
        Longitude:  149o 03' 57.960''E      (149.06610 degrees E)
      In-flight calibration of the data from the interferometer is
        Altitude:   1164 meters
    975            0.99           1200           0.99
      In-flight calibration of the data from the interferometer is
      accomplished using periodic observations of deep space along
 
    980            0.99           1205           1.00
      accomplished using periodic observations of deep space along
      with a precise knowledge of the instrument cavity temperature.
Operational Modes
    985            0.99           1210           1.00
      with a precise knowledge of the instrument cavity temperature.
      Use of the instrument temperature itself as a calibration point
=================
    990            0.98           1215           1.00
      was necessitated because the large size of the telescope made
      Use of the instrument temperature itself as a calibration point
 
    995            0.98           1220           1.00
      the use of an on-board blackbody target impractical.
      was necessitated because the large size of the telescope made
 
      the use of an on-board blackbody target impractical.
Operational modes used:  imaging,  slit spectroscopy, and spectral
 
    The responsivity of the instrument and a spectral instrument
      The calibration is carried out for each wavenumber interval
mapping.  The spectral mapping is done by taking spectra using a slit
      The calibration is carried out for each wavenumber interval
      independently using I = B*(Tinst)*(C2 C1)/C2 where I is the
across the target object and then moving the slit to take the next
    temperature may also be derived from each calibration pair.  The
    noise equivalent spectral radiance (NESR), a measure of the
      independently using I = B*(Tinst)*(C2 C1)/C2 where I is the
spectrum.  Effectively the telescope is scanned perpendicular to the
      calibrated planetary radiance, B*(Tinst) is the Planck radiance
    random errors in the measurements, is calculated from the
      at the instrument temperature Tinst, and C2 and C1 are the
slit direction, while IRIS records spectra at each of a number of
      calibrated planetary radiance, B*(Tinst) is the Planck radiance
    standard deviation of the individual instantaneous
      at the instrument temperature Tinst, and C2 and C1 are the
      spectral amplitudes measured while observing the planet and
positions.  The number of frames taken is thus the number of positions
    responsivities.  The derivation and description of all the
      spectral amplitudes measured while observing the planet and
      deep space, respectively.  This calibration technique requires
required along the scan line, or a multiple thereof for multiple passes
    instrumental parameters are discussed in detail in
      that the interferometer and all elements within its field of
      deep space, respectively.  This calibration technique requires
(for the IRIS SL9 data we typically used 153 cycles, or scan positions,
      that the interferometer and all elements within its field of
    HANELETAL1972D. Reference, responsivity, noise, and instrument
      view, including the telescope mirrors, apertures, and baffles,
comprising 2 passes across the planet).  The scan direction corresponds
      be at precisely the same temperature.  This condition is
    temperature spectra are included in the auxiliary data of the
      view, including the telescope mirrors, apertures, and baffles,
to the z-axis in the output data cube. Consequently increasing pixel
      be at precisely the same temperature.  This condition is
    MARINER9-MARS-IRIS-3-RDR-V1.0 dataset.  Small, narrow spikes are
      insured through the use of thermostatically controlled heaters.
number on the z-axis also corresponds to increasing time since the start
of the scan.
    present in the instrument NESR at the following locations:
      To minimize systematic errors from possible small changes in
      insured through the use of thermostatically controlled heaters.
 
      To minimize systematic errors from possible small changes in
      the instrument responsivity, the calibration must be updated as
      a function of time during the encounter.
    nu(cm-1)      f(Hz)         Probable Source
      the instrument responsivity, the calibration must be updated as
The resulting data cube will have as the other spatial dimensions the
 
      a function of time during the encounter.
    ----------------------------------------------------
128 columns of the chip in the spectral (x) direction (unless windowed
 
     356.          8.36         8-1/3 bps-telemetry rate
smaller - although windowing this axis, i.e. cutting down on the
      During an encounter, the deep space spectra for each day were
     713.         16.76         2 (8-1/3)
      averaged and a time corresponding to the average time was
      During an encounter, the deep space spectra for each day were
recorded spectral range, is VERY rare) and the 128 rows that include
    1069.         25.12         4 (8-1/3)
      averaged and a time corresponding to the average time was
      assigned to each average.  In addition to the daily averages, a
spatial information along the length of slit used (y-axis). Some of our
    1203.         28.27         Unknown
      grand average of all deep space spectra was calculated.  For
data are windowed in y, however, so the full 128 pixels may not have
      assigned to each average.  In addition to the daily averages, a
    1426.         33.52         4 (8-1/3) & 33-1/3
been used.  This form of windowing is normally done to reduce the
      grand average of all deep space spectra was calculated.  For
      each day a ratio spectrum consisting of the daily average power
    1782.         41.88         5 (8-1/3)
      spectrum divided by the grand average power spectrum was used
      each day a ratio spectrum consisting of the daily average power
readout time of the chip and avoid saturation on bright objects (like
 
      to scale the grand average instrument response to obtain the
      spectrum divided by the grand average power spectrum was used
the impacts!).  When cutting the data cube, an image of the scanned
      to scale the grand average instrument response to obtain the
      daily response.  Individual spectra were then calibrated using
    The most probable sources of most of these spikes are transients
planet will be found in the yzplane.  For every pixel in that yzplane
    caused by the engineering telemetry channels which have
      a linear interpolation.  The calibrated spectral radiances are
      daily response.  Individual spectra were then calibrated using
image, a spectra will have been recorded in the x direction. Conversely,
      expressed in Watt/cm**2/sr/cm**-1.
    characteristic frequencies of 8-1/3 and 33-1/3 bps.  The source
      a linear interpolation.  The calibrated spectral radiances are
the xyplane contains a series of spectra with spatial information (along
 
      expressed in Watt/cm**2/sr/cm**-1.
    of the interference at 28.27 Hz is unknown.
the slit, i.e. a slice of the planet) in the y direction.
 
      Radiometer calibration consists of a verification of instrument
Measured Parameters
    In addition to the radiometric calibration, a wave number
      stability by repeated determinations of t(target plate), based
      Radiometer calibration consists of a verification of instrument
===================
    correction has been applied to the data.  The finite solid
      on observations of a diffusely scattering target plate mounted
      stability by repeated determinations of t(target plate), based
 
    angles of the primary and reference interferometers cause a
      on observations of a diffusely scattering target plate mounted
      on the spacecraft.  The calibration conversion to Watts at the
      detector takes into account the detector response and
      on the spacecraft.  The calibration conversion to Watts at the
    small wave number shift and a distortion of the true wave number
The instrument actually measures the brightness of the area of the sky
      detector takes into account the detector response and
      electrical gains.  Observations of the target plate were
the telescope is pointed to in a specific wavelength region for
    scale.  This well known effect, caused by the interference of
      electrical gains.  Observations of the target plate were
imaging, and for a wide range of wavelengths for spectroscopy and
    on-axis and off-axis rays, has been corrected for empirically.
      carried out before and after each encounter with the exception
      of after the Voyager 2 Saturn encounter when jamming of the
    A numerical fit of a Lorentzian function was made to determine
      carried out before and after each encounter with the exception
spectral mapping.  The imaging uses a bandpass filter to only capture
      instrument scan platform caused the maneuver to be aborted.
      of after the Voyager 2 Saturn encounter when jamming of the
    the center wave number position nu_m and nu_t of the strongest
the specific wavelength range desired (example:  2.34um Methane band
 
    carbon dioxide features in a measured and in a theoretical
      instrument scan platform caused the maneuver to be aborted.
filter used for N and V imaging).  The spectra are created by passing
 
    spectrum, respectively.  The correction adopted to provide the
the light from the target through a grism (a grating etched prism)
      The long term behavior of the target calibration data for the
which differentiates the incoming light into its component
    theoretical wave number scale is nu_t = (0.016187 + nu_m) /
      The long term behavior of the target calibration data for the
      two IRIS radiometers is presented in the following tables.  The
wavelengths.
    1.0010602.  This adjustment has been incorporated in the
      observed target signal, corrected for offsets, and normalized
      two IRIS radiometers is presented in the following tables.  The
    calculation of the wave number mesh for the calibrated
      for changes in heliocentric distance, has remained constant
      observed target signal, corrected for offsets, and normalized
    radiances.
      for changes in heliocentric distance, has remained constant
      within quantization uncertainties throughout the mission.  In
 
      within quantization uncertainties throughout the mission.  In
      the absence of compensating changes in the target plate and the
 
      instrument, this implies excellent radiometer stability.  The
      the absence of compensating changes in the target plate and the
  Operational Considerations
      arithmetic average of all target measurements, with a 1.5%
      instrument, this implies excellent radiometer stability.  The
  ==========================
      arithmetic average of all target measurements, with a 1.5%
      uncertainty, is adopted as the normalized target signal for
      uncertainty, is adopted as the normalized target signal for
      purposes of absolute calibration: 30960 +/- 460 DNi x AU**2;
    The Mariner 9 IRIS instrument operated normally throughout the
    mission.  As discussed in the Instrument Calibration
      purposes of absolute calibration: 30960 +/- 460 DNi x AU**2;
      this differs slightly from the published value 31152 +/- 312
    Description, the excellent thermal stability of the Mariner 9
      DNi x AU**2 [PEARL&CONRATH1991].  The target signals for the
      this differs slightly from the published value 31152 +/- 312
    IRIS permitted the entire ensemble of 1766 calibration pairs
      DNi x AU**2 [PEARL&CONRATH1991].  The target signals for the
      integrating, x8 sampling, and x1 sampling radiometer data are
      in the ratio 24:8:1.
      integrating, x8 sampling, and x1 sampling radiometer data are
    acquired during the Mariner mission to be averaged to provide a
 
      in the ratio 24:8:1.
    single set of calibration parameters.  Consequently, the random
 
    Table 2. Target plate calibrations - integrating radiometer
    error introduced into the individual target spectra from the
             (integrating:high_gain:normal_gain=24:8:1)
    Table 2. Target plate calibrations - integrating radiometer
    calibration is extremely small.  However, a detailed analysis of
 
             (integrating:high_gain:normal_gain=24:8:1)
    emission angle pairs of spectra has determined that there may be
 
                                 VG1 Jupiter     VG1 Jupiter
    a very minor calibration error due to a small spike in one of
                                 VG1 Jupiter     VG1 Jupiter
    Calibration Quantity         Pre-encounter   Post-encounter
    the calibration interferograms.  Additionally, for spectra taken
    Calibration Quantity         Pre-encounter   Post-encounter
    ____________________________ _______________ _______________
    of areas with extremely low temperatures the NESR dominates at
    Space before (DN)            9.5 +/- 1.0     17.0 +/- 1.5
    ____________________________ _______________ _______________
    high wavenumbers causing the calculated brightness temperatures
    to increase with increasing wavenumber.
    Space After (DN)             9.0 +/- 0.5     16.0 +/- 0.5
    Space before (DN)            9.5 +/- 1.0     17.0 +/- 1.5
 
    Space After (DN)             9.0 +/- 0.5     16.0 +/- 0.5
    Space weighted mean (DN) [1] 9.1 +/- 0.4     16.1 +/- 0.5
 
    Space weighted mean (DN) [1] 9.1 +/- 0.4     16.1 +/- 0.5
    Raw target (DN) [2]          1157.5 +/- 5.8  1029.5 +/- 5.1
  Instrument Detectors
    Adjusted target (DN) [3]     1148.4 +/- 5.8  1013.4 +/- 5.2
    Raw target (DN) [2]          1157.5 +/- 5.8  1029.5 +/- 5.1
  ====================
    Distance to Sun (10e+8 km)   7.67024         8.10236
    Adjusted target (DN) [3]     1148.4 +/- 5.8  1013.4 +/- 5.2
    Distance to Sun (10e+8 km)   7.67024         8.10236
    The detector of the infrared interferometer is a thermister
    DN x AU**2                   30190. +/- 150. 29730. +/- 150.
 
    bolometer operating at 250 K with a bias voltage of 500 V.
    DN x AU**2                   30190. +/- 150. 29730. +/- 150.
 
 
                                 VG1 Saturn      VG1 Saturn
  Instrument Electronics
                                 VG1 Saturn      VG1 Saturn
    Calibration Quantity         Pre-encounter   Post-encounter
  ======================
    Calibration Quantity         Pre-encounter   Post-encounter
    ____________________________ _______________ _______________
    Space before (DN)            19.5 +/- 0.5    16.25 +/- 0.25
    ____________________________ _______________ _______________
    The bulk of the analog and all of the digital circuitry is in an
    electronics module located in the support base for the
    Space After (DN)             17.5 +/- 0.5    16.5 +/- 0.5
    Space before (DN)            19.5 +/- 0.5    16.25 +/- 0.25
    Space After (DN)             17.5 +/- 0.5    16.5 +/- 0.5
    Space weighted mean (DN) [1] 18.5 +/- 1.0    16.3 +/- 0.2
    interferometer module.  The parity and summation electronics are
    Space weighted mean (DN) [1] 18.5 +/- 1.0    16.3 +/- 0.2
    Raw target (DN) [2]          415.5 +/- 2.1   328.5 +/- 1.6
    in a separate box attached to the support base electronics
    module.  The primary and standby power supplies and the
    Adjusted target (DN) [3]     397.0 +/- 2.3   312.2 +/- 1.7
    Raw target (DN) [2]          415.5 +/- 2.1   328.5 +/- 1.6
    Distance to Sun (10e+8 km)   12.93381        14.66979
    Adjusted target (DN) [3]     397.0 +/- 2.3   312.2 +/- 1.7
    interface chassis are part of the Mariner octagonal spacecraft
    Distance to Sun (10e+8 km)   12.93381        14.66979
    DN x AU**2                   29680. +/- 170. 30020. +/- 160.
    bus structure.  The electronics box contains timing and control
 
    DN x AU**2                   29680. +/- 170. 30020. +/- 160.
    elements, mirror drive circuitry, housekeeping monitors, thermal
 
    controllers, and analog-to-digital converters.
 
                                 VG2 Jupiter     VG2 Jupiter
 
                                 VG2 Jupiter     VG2 Jupiter
    Calibration Quantity         Pre-encounter   Post-encounter
  Instrument Optics
    Calibration Quantity         Pre-encounter   Post-encounter
    ____________________________ _______________ _______________
  =================
    Space before (DN)            59 +/- 2        49.0 +/- 0.5
    ____________________________ _______________ _______________
    Space After (DN)             51 +/- 2        48.0 +/- 0.5
    Space before (DN)            59 +/- 2        49.0 +/- 0.5
    All mirrors of the interferometer are gold coated.  The fixed
    Space After (DN)             51 +/- 2        48.0 +/- 0.5
    Space weighted mean (DN) [1] 55 +/- 4        48.5 +/- 1.0
    interferometer mirror is the entrance pupil for the optical
    system.  It has an effective circular aperture of 3.5 cm
    Space weighted mean (DN) [1] 55 +/- 4        48.5 +/- 1.0
    Raw target (DN) [2]          1315.0 +/- 6.6  992.5 +/- 5.0
    Adjusted target (DN) [3]     1260.0 +/- 7.7  944.0 +/- 5.1
    Raw target (DN) [2]          1315.0 +/- 6.6  992.5 +/- 5.0
    diameter.  An ellipsoidal mirror collects the energy from the
    Distance to Sun (10e+8 km)   7.43461         8.60397
    Adjusted target (DN) [3]     1260.0 +/- 7.7  944.0 +/- 5.1
    interferometer and focuses it onto the infrared detector, a
    Distance to Sun (10e+8 km)   7.43461         8.60397
    thermister bolometer, which serves as the exit pupil.
    DN x AU**2 [4]               31120. +/- 190. 31230. +/- 170.
 
    DN x AU**2 [4]               31120. +/- 190. 31230. +/- 170.
 
 
  Instrument Offset
                                 VG2 Saturn      VG2 Saturn
  =================
                                 VG2 Saturn      VG2 Saturn
    Calibration Quantity         Pre-encounter   Post-encounter
    Calibration Quantity         Pre-encounter   Post-encounter
    ____________________________ _______________ _______________
    The instrument and the associated electronics modules are bolted
    Space before (DN)            51.0 +/- 1.0          [5]
    ____________________________ _______________ _______________
    to the scan platform.  The primary and standby power supplies
    Space After (DN)             47.0 +/- 1.5          [5]
    Space before (DN)            51.0 +/- 1.0          [5]
    and the interface chassis are part of the octagonal electronics
    Space After (DN)             47.0 +/- 1.5          [5]
    Space weighted mean (DN) [1] 49.0 +/- 2.0          [5]
    rack of the spacecraft.  The instrument is approximately
    bore-sighted with the television camera, ultraviolet
    Raw target (DN) [2]          455.5 +/- 2.3         [5]
    Space weighted mean (DN) [1] 49.0 +/- 2.0          [5]
    spectrometer and infrared radiometer.
    Adjusted target (DN) [3]     406.5 +/- 3.0         [5]
    Raw target (DN) [2]          455.5 +/- 2.3         [5]
 
    Adjusted target (DN) [3]     406.5 +/- 3.0         [5]
    Distance to Sun (10e+8 km)   13.08739              [5]
 
    DN x AU**2 [4]               31110. +/- 230.       [5]
    Distance to Sun (10e+8 km)   13.08739              [5]
 
  Instrument Parameters
    DN x AU**2 [4]               31110. +/- 230.       [5]
 
  =====================
 
    Thermal Radiance (W cm-2 ster-1/cm-1).
                                 VG2 Uranus      VG2 Uranus
 
                                 VG2 Uranus      VG2 Uranus
    Calibration Quantity         Pre-encounter   Post-encounter
 
    Calibration Quantity         Pre-encounter   Post-encounter
    ____________________________ _______________ _______________
  Instrument Modes
    Space before (DN)            52.0 +/- 0.5    53.0 +/- 0.5
    ____________________________ _______________ _______________
  ================
    Space After (DN)             51.5 +/- 1.0    53.0 +/- 0.5
    Space before (DN)            52.0 +/- 0.5    53.0 +/- 0.5
    Space After (DN)             51.5 +/- 1.0    53.0 +/- 0.5
    Space weighted mean (DN) [1] 51.9 +/- 0.4    53.0 +/- 0.5
    The instrument possesses only one operating mode.  When turned
    Space weighted mean (DN) [1] 51.9 +/- 0.4    53.0 +/- 0.5
    Raw target (DN) [2]          143.5 +/- 0.7   138.0 +/- 0.7
    on the instruments acquires one interferogram every 21 second
    data frame.
    Adjusted target (DN) [3]     91.6 +/- 0.8    85.0 +/- 0.9
    Raw target (DN) [2]          143.5 +/- 0.7   138.0 +/- 0.7
 
    Distance to Sun (10e+8 km)   27.34484        28.88645
    Adjusted target (DN) [3]     91.6 +/- 0.8    85.0 +/- 0.9
    Distance to Sun (10e+8 km)   27.34484        28.88645
    DN x AU**2 [4]               30610. +/- 280. 31690. +/- 320.
 
    DN x AU**2 [4]               30610. +/- 280. 31690. +/- 320.
 
 
                                 VG2 Neptune     VG2 Neptune
                                 VG2 Neptune     VG2 Neptune
    Calibration Quantity         Pre-encounter   Post-encounter
    Calibration Quantity         Pre-encounter   Post-encounter
    ____________________________ _______________ _______________
    Space before (DN)            53.0 +/- 0.5    52.5 +/- 0.5
    ____________________________ _______________ _______________
    Space After (DN)             53.0 +/- 0.5    52.5 +/- 1.0
    Space before (DN)            53.0 +/- 0.5    52.5 +/- 0.5
    Space After (DN)             53.0 +/- 0.5    52.5 +/- 1.0
    Space weighted mean (DN) [1] 53.0 +/- 0.5    52.5 +/- 0.4
    Raw target (DN) [2]          95.8 +/- 0.5    86.3 +/- 0.8
    Space weighted mean (DN) [1] 53.0 +/- 0.5    52.5 +/- 0.4
    Adjusted target (DN) [3]     42.8 +/- 0.7    33.8 +/- 0.9
    Raw target (DN) [2]          95.8 +/- 0.5    86.3 +/- 0.8
    Distance to Sun (10e+8 km)   39.6584         45.2993
    Adjusted target (DN) [3]     42.8 +/- 0.7    33.8 +/- 0.9
    Distance to Sun (10e+8 km)   39.6584         45.2993
    DN x AU**2 [4]               30040. +/- 500. 30940. +/- 800.
 
    DN x AU**2 [4]               30040. +/- 500. 30940. +/- 800.
 
    ____________________________________________________________
    Notes:
    ____________________________________________________________
    Notes:
    [1] Where the difference between pre-encounter and
    [1] Where the difference between pre-encounter and
        post-encounter measurements of space exceeds the random
        baseline variation, the average is taken as the
        post-encounter measurements of space exceeds the random
        baseline variation, the average is taken as the
        arithmetic mean, with the difference as the uncertainty.
        arithmetic mean, with the difference as the uncertainty.
    [2] Considers the larger of 0.5% (estimated maximum possible
        nonlinearity) or the baseline variation as the
    [2] Considers the larger of 0.5% (estimated maximum possible
        uncertainty.
        nonlinearity) or the baseline variation as the
        uncertainty.
    [3] All uncertainties are considered uncorrelated in
        calculation of the adjusted target signal.
    [3] All uncertainties are considered uncorrelated in
        calculation of the adjusted target signal.
    [4] For Voyager 2 only, the adopted mean value of 30960 +/-
        460 is entered for all cases in the calibration files.
    [4] For Voyager 2 only, the adopted mean value of 30960 +/-
    [5] For Voyager 2 Saturn post-encounter, the instrument
        460 is entered for all cases in the calibration files.
    [5] For Voyager 2 Saturn post-encounter, the instrument
        platform jammed so the calibration maneuver was aborted.
 
        platform jammed so the calibration maneuver was aborted.
 
 
      Because the spectral transmission of the radiometer is not flat
      Because the spectral transmission of the radiometer is not flat
      across the bandwidth, further calibration requires knowledge of
      the relative spectrum of each object observed.  The absolute
      across the bandwidth, further calibration requires knowledge of
      the relative spectrum of each object observed.  The absolute
      reflectance of the Voyager 1 and 2 target plates are 0.502 +/-
      0.018 and 0.497 +/- 0.018, respectively.  A detailed
      reflectance of the Voyager 1 and 2 target plates are 0.502 +/-
      0.018 and 0.497 +/- 0.018, respectively.  A detailed
      description of a technique for calibrating the radiometer is
      given in [HANELETAL1981A].
      description of a technique for calibrating the radiometer is
 
      given in [HANELETAL1981A].
 
 
    Instrument Detectors
    ====================
    Instrument Detectors
    ====================
      The detector of the broadband reflected solar radiometer is an
      eighteen-junction thermopile with a 3 second thermal time
      The detector of the broadband reflected solar radiometer is an
      constant and is operated at a temperature of 200 K.  The
      eighteen-junction thermopile with a 3 second thermal time
      constant and is operated at a temperature of 200 K.  The
      thermopile used with the broadband radiometer has a noise
      equivalent power of 4E-10 Watt/Hz**1/2.
      thermopile used with the broadband radiometer has a noise
 
      equivalent power of 4E-10 Watt/Hz**1/2.
 
      The detector of the infrared interferometer is a low-impedance
      Schwartz-type four-junction thermopile with a thermal time
      The detector of the infrared interferometer is a low-impedance
      Schwartz-type four-junction thermopile with a thermal time
      constant of 12 millisecond.  and is operated at a temperature
      of 200 K.  The thermopile used with the interferometer has a
      constant of 12 millisecond.  and is operated at a temperature
      noise equivalent power of approximately 2E-10 Watt/Hz**1/2.
      of 200 K.  The thermopile used with the interferometer has a
 
      noise equivalent power of approximately 2E-10 Watt/Hz**1/2.
 
 
    Instrument Electronics
    ======================
    Instrument Electronics
    ======================
      The bulk of the analog and all of the digital circuitry is
      located in an electronics module separate form the
      The bulk of the analog and all of the digital circuitry is
      located in an electronics module separate form the
      interferometer module.  The power supply is located in still
      interferometer module.  The power supply is located in still
      another box.  Only elements that had to be close to detectors
      to minimize noise, such as the sensors for temperature
      another box.  Only elements that had to be close to detectors
      to minimize noise, such as the sensors for temperature
      measurements and controls, were located in the optics module.
      The electronics box contains timing and control elements,
      measurements and controls, were located in the optics module.
      mirror drive circuitry, housekeeping monitors, thermal
      The electronics box contains timing and control elements,
      mirror drive circuitry, housekeeping monitors, thermal
      controllers, analog-to-digital converters, and spacecraft
      controllers, analog-to-digital converters, and spacecraft
      interface circuits.  The power module contains one primary and
      interface circuits.  The power module contains one primary and
      two auxiliary power supplies that convert spacecraft primary ac
      into dc voltages required to operate the instrument.  One of
      two auxiliary power supplies that convert spacecraft primary ac
      into dc voltages required to operate the instrument.  One of
      the auxiliary supplies is always on to maintain the instrument
      the auxiliary supplies is always on to maintain the instrument
      at the proper temperature.  The primary power supply is on only
      when the instrument is on during tests, calibrations and
      at the proper temperature.  The primary power supply is on only
      when the instrument is on during tests, calibrations and
      observation periods during planetary encounters.  Because of
      the requirement to pass through the Jovian radiation
      observation periods during planetary encounters.  Because of
      the requirement to pass through the Jovian radiation
      environment, hardened electronics components were used where
      environment, hardened electronics components were used where
      possible.  The bulk of the instrument electronics consists of
      possible.  The bulk of the instrument electronics consists of
      radiation-hardened integrated circuits.  A description of the
      electronics, along with a block diagram, is given in
      radiation-hardened integrated circuits.  A description of the
      [HANELETAL1980A].
      electronics, along with a block diagram, is given in
 
      [HANELETAL1980A].
 
 
    Instrument Optics
    =================
    Instrument Optics
    =================
      The Cassegrain telescope has a parabolic primary mirror 50 cm
      The Cassegrain telescope has a parabolic primary mirror 50 cm
      in diameter with a 7.62 cm hyperbolic secondary mirror, and an
      effective focal length of 303.5 cm and an F number of 6.07.  A
      in diameter with a 7.62 cm hyperbolic secondary mirror, and an
      dichroic mirror divides the beam from the telescope into two
      effective focal length of 303.5 cm and an F number of 6.07.  A
      dichroic mirror divides the beam from the telescope into two
      separate beams, one going to the infrared interferometer and
      the other to the broadband reflected solar radiometer.  The
      separate beams, one going to the infrared interferometer and
      the other to the broadband reflected solar radiometer.  The
      telescope mirrors and support structure, like most of the other
      mechanical parts of the instrument, are made of optical-grade
      telescope mirrors and support structure, like most of the other
      beryllium.  The primary mirror is gold coated over a nickel
      mechanical parts of the instrument, are made of optical-grade
      beryllium.  The primary mirror is gold coated over a nickel
      plating.  The secondary mirror has an aluminum coating over the
      nickel plating, and this in turn is overcoated with silicon
      plating.  The secondary mirror has an aluminum coating over the
      monoxide for protection.
      nickel plating, and this in turn is overcoated with silicon
 
      monoxide for protection.
 
 
    Instrument Offset
    =================
    Instrument Offset
    =================
      The instrument and the associated electronics and power supply
      modules are bolted to the scan platform.  The telescope is
      The instrument and the associated electronics and power supply
      approximately bore-sighted with the wide and narrow angle
      modules are bolted to the scan platform.  The telescope is
      approximately bore-sighted with the wide and narrow angle
      television cameras, and with the PPS and UVS instruments.
 
      television cameras, and with the PPS and UVS instruments.
 
 
    Instrument Parameters
    =====================
    Instrument Parameters
    =====================
      The following instrument parameters are measured.
 
      The following instrument parameters are measured.
 
      Sampled Visible Radiance - Series of 8 radiometer samples taken
      during a 48 second data frame with the high gain channel.  The
      Sampled Visible Radiance - Series of 8 radiometer samples taken
      quantity given is power at the detector in Watts.  (-1.0
      during a 48 second data frame with the high gain channel.  The
      indicates data off the planet).
      quantity given is power at the detector in Watts.  (-1.0
 
      indicates data off the planet).
 
      Integrated Visable Radiance - The broadband, reflected solar
      Integrated Visable Radiance - The broadband, reflected solar
      radiometer signal integrated over the 45.6 seconds that IRIS
      radiometer signal integrated over the 45.6 seconds that IRIS
      data are taken within the 48 second data frame.  The quantity
      given is power at the detector in Watts.
      data are taken within the 48 second data frame.  The quantity
 
      given is power at the detector in Watts.
 
      Thermal Radiance - Radiance (W cm-2 ster-1) within a 4.3 cm-1
      spectral interval.
      Thermal Radiance - Radiance (W cm-2 ster-1) within a 4.3 cm-1
 
      spectral interval.
 
 
    Instrument Modes
    ================
    Instrument Modes
    ================
      The instrument possesses only one operating mode.  When turned
      on the instruments acquires one interferogram every 48 second
      The instrument possesses only one operating mode.  When turned
      data frame.  In addition data from the reflected solar
      on the instruments acquires one interferogram every 48 second
      data frame.  In addition data from the reflected solar
      radiometer are also obtained every data frame.  The latter
      radiometer are also obtained every data frame.  The latter
      consist of a measurement integrated over 45.6 seconds as well
      as 8 samples of both high and normal gain measurements
      consist of a measurement integrated over 45.6 seconds as well
      as 8 samples of both high and normal gain measurements
      distributed at 6 second intervals throughout the data frame.
 
      distributed at 6 second intervals throughout the data frame.
 
 
REFERENCE_DESCRIPTION Hanel, R., B. Schlachman, E. Breihan, R. Bywaters, F. Chapman, M. Rhodes,D. Rodgers, D. Vanous, Mariner 9 Michelson Interferometer, Applied Optics,11, 2625, 1972.

Hanel, R., B. Conrath, W. Hovis, V. Kunde, P. Lowman, J. Pearl, C.Prabhakara, B. Schlachman, Infrared Spectroscopy Experiment on the Mariner9 Mission: Preliminary Results, Science, 175, 305-308, 1972.

Hanel, R., B. Conrath, W. Hovis, V. Kunde, P. Lowman, W. Maguire, J. Pearl,J. Pirraglia, C. Prabhakara, B. Schlachman, Investigation of the MartianEnvironment by Infrared Spectroscopy, Icarus, 17, 423-442, 1972.

Hanel, R., B. Conrath, V. Kunde, C. Prabhakara, I. Revah, V. Salomonson, G.Wolford, The Nimbus 4 Infrared Spectroscopy Experiment 1: CalibratedThermal Emission Spectra, Journal of Geophysical Research, 77, 2629, 1972.

Hanel, R.A., D. Crosby, L.W. Herath, D. Vanous, D.Collins, H. Creswick, C. Harris, and M. Rhodes, InfraredSpectrometer for Voyager, Applied Optics, 19, 1391-1400,1980.

Hanel, R.A., B.J. Conrath, L.W. Herath, V.G. Kunde, andJ.A. Pirraglia, Albedo, Internal Heat, and Energy Balanceof Jupiter: Preliminary Results of the Voyager InfraredInvestigation, J. Geophys. Res., 86, 8705-8712, 1981.

N/A

Pearl, J.C., and B.J. Conrath, The Albedo, EffectiveTemperature, and Energy Balance of Neptune, as Determinedfrom Voyager Data, J. Geophys. Res., 96, 18, 921-18, 930,1991.