Abstract

The Michelson interferometer on Mariner 9 measures the thermal emission spectrum of Mars between 200 cm−1 and 2000 cm−1 (between 5 μm and 50 μm) with a spectral resolution of 2.4 cm−1 in the apodized mode. A noise equivalent radiance of 0.5 × 10−7 W cm−2 sr−1/cm−1 is deduced from data recorded in orbit around Mars. The Mariner interferometer deviates in design from the Nimbus 3 and 4 interferometers in several areas, notably, by a cesium iodide beam splitter and certain aspects of the digital information processing. Special attention has been given to the problem of external vibration. The instrument performance is demonstrated by calibration data and samples of Mars spectra.

© 1972 Optical Society of America

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References

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  1. Icarus 12(1) (1970).
  2. Science 1754019 (1972).
  3. R. A. Hanel, B. Schlachman, F. D. Clark, C. H. Prokesb, J. B. Taylor, W. M. Wilson, L. Chaney, Appl. Opt. 9, 1767 (1970).
    [CrossRef] [PubMed]
  4. R. A. Hanel, B. Schlachman, D. Rodgers, D. Vanous, Appl. Opt. 10, 1376 (1971).
    [CrossRef] [PubMed]
  5. B. J. Conrath, R. A. Hanel, V. G. Kunde, C. Prabhakara, J. Geophys. Res. 75, 5831 (1970).
    [CrossRef]
  6. R. A. Hanel, B. J. Conrath, Nature 228, 143 (1970).
    [CrossRef] [PubMed]
  7. J. Connes, Rev. Opt. Theor. Instrum. 40, 45, 116, 171, 231 (1961).
  8. R. B. Blackman, J. W. Tukey, The Measurement of Power Spectra (Dover, New York, 1958).
  9. B. Dorsch, Warner H. Miller, Error Control Using a Concatenated Code, NASA Tech. Note NASA TN D-5775 (June1970).

1972 (1)

Science 1754019 (1972).

1971 (1)

1970 (5)

Icarus 12(1) (1970).

B. Dorsch, Warner H. Miller, Error Control Using a Concatenated Code, NASA Tech. Note NASA TN D-5775 (June1970).

R. A. Hanel, B. Schlachman, F. D. Clark, C. H. Prokesb, J. B. Taylor, W. M. Wilson, L. Chaney, Appl. Opt. 9, 1767 (1970).
[CrossRef] [PubMed]

B. J. Conrath, R. A. Hanel, V. G. Kunde, C. Prabhakara, J. Geophys. Res. 75, 5831 (1970).
[CrossRef]

R. A. Hanel, B. J. Conrath, Nature 228, 143 (1970).
[CrossRef] [PubMed]

1961 (1)

J. Connes, Rev. Opt. Theor. Instrum. 40, 45, 116, 171, 231 (1961).

Blackman, R. B.

R. B. Blackman, J. W. Tukey, The Measurement of Power Spectra (Dover, New York, 1958).

Chaney, L.

Clark, F. D.

Connes, J.

J. Connes, Rev. Opt. Theor. Instrum. 40, 45, 116, 171, 231 (1961).

Conrath, B. J.

R. A. Hanel, B. J. Conrath, Nature 228, 143 (1970).
[CrossRef] [PubMed]

B. J. Conrath, R. A. Hanel, V. G. Kunde, C. Prabhakara, J. Geophys. Res. 75, 5831 (1970).
[CrossRef]

Dorsch, B.

B. Dorsch, Warner H. Miller, Error Control Using a Concatenated Code, NASA Tech. Note NASA TN D-5775 (June1970).

Hanel, R. A.

Kunde, V. G.

B. J. Conrath, R. A. Hanel, V. G. Kunde, C. Prabhakara, J. Geophys. Res. 75, 5831 (1970).
[CrossRef]

Miller, Warner H.

B. Dorsch, Warner H. Miller, Error Control Using a Concatenated Code, NASA Tech. Note NASA TN D-5775 (June1970).

Prabhakara, C.

B. J. Conrath, R. A. Hanel, V. G. Kunde, C. Prabhakara, J. Geophys. Res. 75, 5831 (1970).
[CrossRef]

Prokesb, C. H.

Rodgers, D.

Schlachman, B.

Taylor, J. B.

Tukey, J. W.

R. B. Blackman, J. W. Tukey, The Measurement of Power Spectra (Dover, New York, 1958).

Vanous, D.

Wilson, W. M.

Appl. Opt. (2)

Error Control Using a Concatenated Code (1)

B. Dorsch, Warner H. Miller, Error Control Using a Concatenated Code, NASA Tech. Note NASA TN D-5775 (June1970).

Icarus (1)

Icarus 12(1) (1970).

J. Geophys. Res. (1)

B. J. Conrath, R. A. Hanel, V. G. Kunde, C. Prabhakara, J. Geophys. Res. 75, 5831 (1970).
[CrossRef]

Nature (1)

R. A. Hanel, B. J. Conrath, Nature 228, 143 (1970).
[CrossRef] [PubMed]

Rev. Opt. Theor. Instrum. (1)

J. Connes, Rev. Opt. Theor. Instrum. 40, 45, 116, 171, 231 (1961).

Science (1)

Science 1754019 (1972).

Other (1)

R. B. Blackman, J. W. Tukey, The Measurement of Power Spectra (Dover, New York, 1958).

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Figures (10)

Fig. 1
Fig. 1

Transfer functions of the electronic filter, the numerical filter, and their combined effect. The primary sample frequency fs is 675 Hz, and the word rate after summation fw is 225 Hz.

Fig. 2
Fig. 2

Predicted probabilities of bit and frame errors as functions of date in orbit. Position 2 refers to a second position of the high gain spacecraft antenna. Beginning in mid-January, position 2 is more favorable because of spacecraft orientation with respect to the earth–Mars line.

Fig. 3
Fig. 3

IRIS components. In the center is the optical module with the temperature control surface exposed. The electronics modules in the foreground are part of the Mariner octagonal structure. The maximum distance between the Michelson mirror drive and the detector assembly is about 50 cm.

Fig. 4
Fig. 4

IRIS M installed on the Mariner 9 scan platform. The rectangular flexible shield extending from the IRIS (lower right) shades the cooling surface of IRIS from the heat flux of Mars. The large aperture next to IRIS is the telescope of the narrow-angle television camera. Then comes the rectangular aperture of the uv spectrometer, the small lens of the wide-angle camera, and finally the aperture of the ir radiometer.

Fig. 5
Fig. 5

Spectral responsivity of IRIS M for several time periods indicated in the figure. The curves have been displaced in the vertical to facilitate comparison. No significant change of the responsivity with time was observed.

Fig. 6
Fig. 6

NER of IRIS M computed from the repeatability of individual pairs of warm and cold calibration spectra. The smoothness of each curve depends on the total number of calibration pairs used in the computation.

Fig. 7
Fig. 7

Thermal emission spectra recorded over the south polar area of Mars. The early spectrum [revolution 30 (R30)] includes a smaller fraction of the polar ice cap than the later spectrum [revolution 116 (R116)], hence the over-all equivalent brightness temperatures of R30 are higher. The CO2 emission between 600 cm−1 and 750 cm−1 and the SiO2 feature between 800 cm−1 and 1400 cm−1 indicate warmer atmospheric layers and more dust in the early spectrum than in the later one. Rotational water vapor lines are observable in both spectra.

Fig. 8
Fig. 8

Midlatitude spectrum recorded during the early part of the emission (December 1971) under dusty conditions. Atmospheric lapse rates were smaller at that time than later, hence only a shallow structure in the 667-cm−1 CO2 band. Features associated with SiO2 bearing minerals are visible between 400 cm−1 and 600 cm−1 and between 850 cm−1 and 1300 cm−1. The detail shape of these features will be slightly affected by the final calibration procedure.

Fig. 9
Fig. 9

Midlatitude spectrum recorded in March 1972, after most of the mineral dust had settled. The stronger contrast in the 667-cm − CO2 band indicates warmer surface temperatures and cooler upper layers. In spite of the larger lapse rate, the SiO2 features have diminished. Curves of equivalent brightness temperatures (Planck function) are shown for comparison. The temperatures are given in Kelvins.

Fig. 10
Fig. 10

Spectrum recorded over the north polar area. The background temperature of about 145 K indicates a surface at about that temperature; 145 K is the condensation temperature of CO2 at pressures appropriate for Mars. The higher temperatures measured above the cold layer, as indicated by the 667-cm−1 CO2 band structure in emission, are evidence of warmer atmospheric layers above the cold layer, tentatively identified as the polar hood.

Tables (1)

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Table I Characteristic Parameters of Nimbus and Mariner Interferometers

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