Citation
Abstract
Radio noise emissions seen by a spacecraft orbiting Mars or a lander located on the Martian surface are expected to be from Mars’ atmospheric emission, surface noise, and extra-Martian sources. Compared with Earth, Mars has lower surface temperatures and much lower atmospheric absorption and radiation. However, Mars has higher surface emissivity due to the roughness of soil and rocks. Because of very low atmospheric density and optical depth, Mars’ atmospheric emission from oxygen and water vapor is almost negligible. The upwelling brightness temperature at Mars is caused mainly by its surface temperature, with strong local time and latitudinal dependence. Downwelling brightness temperature is dominated by sky temperature. The actual radio noise contributing to the antenna temperature is also a function of antenna orientation, elevation angle, and gain pattern. Assuming a dish antenna with 1-m diameter, for a downward-looking antenna the total noise temperature is about the same as the Earth’s for all frequency bands of interest, with ±15 percent deviations. For an upward-looking antenna, the noise temperature is less than half that of Earth.
Keywords
Details
- Volume
- 42-149
- Published
- May 15, 2002
- Pages
- 1–15
- File Size
- 264.5 KB