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Availability: Archived at NSSDC, accessible from elsewhere


This description was generated automatically using input from the Planetary Data System.

Data Set Overview ================= The dataset contains measurements from the infrared interferometer spectrometer and ancillary data. Each record of the dataset consists of a header and a spectral observation of Mars; the header contains pointing and other information on the geometry of the observation. The dataset is ordered by time as measured by the Data Acquisition System (DAS) time (1 DAS count is approximately 1.2 sec.). Two IRIS frames are completed every 35 DAS counts; every eighth IRIS frame is devoted to a calibration observation (alternately of interstellar space and an internal calibration blackbody), and is therefore absent from the calibrated dataset. The spectral data consist of calibrated thermal emission spectra expressed as spectral radiances in Watt/cm**2/sr/cm**-1. The wavenumber corresponding to each spectral radiance value is not included in the dataset; the beginning wavenumber and the constant wavenumber increment are given, permitting easy calculation of the appropriate wavenumber for each radiance. The calibrated radiances have been obtained from the directly measured interferograms of Mars, along with the deep space and internal blackbody calibration observations. The interferograms are first symmetrized to correct for the fact that they are not sampled at zero path difference, and to remove the asymmetry due to residual dispersion in the beamsplitter and compensator. The symmetrized interferograms are then apodized using a Hamming function, and are cosine transformed. The responsivity obtained from the deep space and internal blackbody measurements is then used to obtain calibrated radiances.

Mariner 9 was placed in a 12 hour orbit about Mars at Lsubs=293, with data transmitted in real time during a 2 hour period around periapsis. The 12 hour period was selected to assure that the spacecraft was always visible from the single large receiving antenna at Goldstone, California once per day (the even numbered orbits). Data from alternate (odd numbered) orbits was received by a smaller antenna at Madrid, Spain; the lower signal-to-noise ratio in these data resulted in numerous 'spikes' in the IRIS interferograms, and a correspondingly high rejection rate during processing. Consequently, very few Martian spectra were obtained on odd numbered orbits. In addition, after 107 days (Lsubs=353), the changing planetary alignments moved the earth off of the transmitting antenna pattern; thereafter, only data that had been recorded were obtained, since transmission required a spacecraft maneuver to target the earth. Consequently, only a handful of data were received from Lsubs=5 to the end of mission at Lsubs=98. As a general overview of the dataset, the distribution of IRIS data in latitude as a function of solar heliocentric longitude is shown in [DOCUMENT/MR9_LS.PDF] and [DOCUMENT/MR9_LS.PS] and the distribution of IRIS data in latitude as a function of martian local time is shown in [DOCUMENT/MR9_LT.PDF] and [DOCUMENT/MR9_LT.PS].

These data are available on-line from the Planetary Data System (PDS) at:

Alternate Names

  • MR9-M-IRIS-3-RDR-V1.0


  • Planetary Science: Atmospheres

Additional Information



Questions and comments about this data collection can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Rudolf A. HanelData ProviderNASA Goddard Space Flight Center
Dr. John C. PearlGeneral ContactNASA Goddard Space Flight
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