Mars Balloon Relay (MBR)
The Mars Balloon Relay, or MBR, was planned to augment the return of data from the penetrators and surface stations of the Russian Mars '94 mission and from penetrators, surface stations, a rover, and a balloon from the Mars '96 mission. The Russian orbiters were to provide the primary data return from these missions. The principal objectives of these experiments were to: (1) obtain high-resolution panoramic surface views; (2) study near-surface properties of the atmosphere; and, (3) study surface and subsurface geology.
In orbit, the MBR was to transmit a continuous 437 MHz signal to the surface, to be received by the Mars '94 and '96 landers and balloon. When the signal strength reached a threshold value, indicating the MBR was close enough to receive a signal, the packages were to transmit their stored data to the MBR on one of two channels (401 or 405 MHz). The MBR in turn would demodulate the signal, measure the Doppler shift for localization and balloon tracking, and send the data, along with its own engineering data, to the memory buffer of the Mars Observer Camera for later retransmission to Earth. There were two contact periods planned per day, each of approximately 11 minutes duration, at 2 a.m. and 2 p.m. local time. The MBR antenna was of quadrifilar helix design with a 65 degree conical pattern, rigidly mounted. The MBR electronics consisted of a UHF coherent receiver, a Viterbi decoder, a Doppler unit, and a memory module.
Contact with Mars Observer was lost for unknown reasons on August 21, 1993, three days before scheduled orbit insertion, so no data were returned for this investigation. This experiment has been re-scheduled to fly on the Mars Global Surveyor.