We have performed a study on telecommunication systems for a hypothetical mission to Mars. The objective cf the study was to evaluate and compare the benefits that microwave (X-band and Ks-band) and Optical communications technologies afford to future missions. The telecommunication systems were required to ietum data after launch and in-orbit at 2.7 AU with daily data volumes ofO.1, 1, or 10 Gbits. Space-borne terminals capable of delivering each of the three data rates were proposed and characterized in terms of mass, power consumption, size, and cost. The estimated paimeters for Xband, Ka-band, and Optical frequencies are compared and presented here. For data volumes ofO.1 and 1 Giga-bit per day, the X-band downlink system has a mass 1.5 times that ofKa-band, and 2.5 times that of Optical system. Ka-band offeied about 20% power saving at 10 Gbit/day over X-band. For all data volumes, the optical communication terminals were lower in mass than the RF terminals. For data volumes of 1 and 10 Gb/day, the space-borne optical terminal also had a lower required DC power. In all three cases, optical communications had a slightly higher development cost for the space terminal.
The recent decision to send two rovers to Mars in 2003 has provided new direction for Mars exploration. To meet these future challenges, NASA's Jet Propulsion Laboratory (JPL) is preparing the Deep Space Network (DSN) and other communication systems to support the expected increase in Mars exploration activities. Toward this end, JPL is conducting studies to enhance communications and navigation capabilities on or around Mars for future Mars missions and is investing in hardware development for use by those missions. One such study is developing a multiple-access scheme and a frequencyutilization plan for in-situ communications and navigation. The results of this study will provide recommendations for developing communications hardware for future Mars missions, establishing interoperability processes and standards, ensuring access to the radio frequency spectrum for operations at Mars and for testing at Earth, and designing a communication and navigation infrastructure around Mars. This paper will focus on the selection of frequencies for local ("in situ'') links at Mars. Various factors affecting the selection of frequencies, including link performance, propagation effects, and mission scenarios, will be discussed.
Preliminary reduction of Viking bistatic radar data gives root-mean-square surface slopes in the Hellas basin on Mars of about 4 degrees on horizontal scales averaged over 10 centimeters to 100 meters. This roughness decreases slightly with position along the ground track, south to north. The dielectric constant in this area appears to be approximately 3.1, greater than the martian average. These values are characteristic of lunar maria and are similar to those found near the Viking lander site in Chryse with the use of Earth-based radar.
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