Spaceborne Telescope for Communication, Ranging, and Imaging

A report describes a program to develop a multi-function telescope to be carried aboard spacecraft of the planned X2000 series of planetary missions. [A related multi-function telescope was described in "Telescope for Imaging and Laser Communication" (NPO-20388), NASA Tech Briefs, Vol. 24, No. 1 (January, 2000), page 27a.] An important element of this program is minimization of instrument mass through combination of several optoelectronic subsystems into one telescope system with one aperture for transmission and reception of light. The functions to be performed by the telescope system include scientific imaging, reception of laser-altimeter return signals, and two-way optical communication. The communication functions include transmission of scientific data, reception of commands, and reception and retransmission of laser ranging signals. For communication, the telescope would be aimed at the sunlit Earth, by use of aiming techniques like those summarized in the cited previous article. Rates for transmission of scientific data to Earth from as far away as Jupiter would range from 100 kb/s (day) to 400 kb/s (night). The data rate for reception of commands from Earth would be 2 kb/s. A flight-qualified engineering model of the system is scheduled for completion in the year 2001.