Comparative study of optical and rf communication systems for a Mars mission

Abstract

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.

<title>Optical communications study for the Next-Generation Space Telescope</title>

“…The estimates for the proposed NGST system are the estimates for the 10-cm system listed in [3]. A major difference in the between the system in [3] and the proposed system is that the transmitting laser for NGST is a solid state laser with a MOPA instead of a Q-switched pumped laser.…”

“…Identification of the position of the Earth receiving station to better than 5 to 10% of the downlink signal beamwidth is desired to insure a stable link. Once the position of the receiving station is known the point-ahead angle for the downlink beam can be determined such that the signal from the spacecraR is received by the ground station [3]. The acquisition and tracking for the optical communication system is performed by tracking a laser beacon signal sent by the earth receiving station.…”

“…The diameters of the primary mirrors for the ground telescopes are 10-m and 3-m. Each of these telescopes will have an obscuration of 20°'0. More detailed descriptions of the ground and space telescopes, complete with mass and cost estimates are found in [3 ]. …”

“…Costing for components is based on 1998 Dollars. Mass, power, and cost estimates rely heavily on data obtained in [3].…”

Design and early development of a UAV terminal and a ground station for laser communications

“…A free-space lasercom system does not have to compete for electromagnetic broadcast bands in the spectrum at all. Another big advantage of this technology is that it enables lower power consumption and smaller and lighter terminals [7]. Since a first-class goal in the SINTONIA program is developing low-impact technology onboard UAVs, optical communications fit ideally these requirements.…”