NASA begins work on radio transmitters for Mars Ascent Vehicle

NASA’s Marshall Space Flight Center (MSFC) in Huntsville, Ala., is soliciting information from potential sources for the manufacturing of Radio Frequency (RF) Transmitters for the Mars Ascent Vehicle (MAV). The space agency made the announcement in a Request For Information contract document released Thursday.

The MAV is one part of the Mars Sample Return Campaign and is a joint effort between MSFC and the Jet Propulsion Laboratory in Pasadena, Calif. The MAV is a vehicle designed to launch from the surface of Mars and will transport Mars samples taken from the Martian surface and launch the payload into orbit for rendezvous with an orbiting spacecraft. The Earth Return Orbiter (ERO) will rendezvous with and capture the payload from orbit, and bring it back to earth.

The MAV transmitter will transmit navigation and vehicle health data during the flight from launch until stage separation in order to aide in the capture of the released payload. The MAV has a downlink/transmit-only requirement for RF communications during the mission. There is currently no uplink/receive signal requirement. Therefore, only the manufacture of a device with data transmitting capabilities will be required. The transmitter will operate without any return link signal.  The transmitter will be required to operate solely in transmitting data mode during the first stage of the flight. The transmitter shall be able to switch between transmitting data mode, CW continuous mode, and CW pulse mode upon receiving a command from the flight computer.

RF Transmitter Specifications and Characteristics

• Mode of Operation:  Transmit Data
• Mode of Operation:  Carrier-only CW
• Mode of Operation:  Carrier Pulses
• Frequency:  401.585625 MHz
• Information Rate (prior to any encoding applied):  8 kbps
• Coded Symbol Rate (after all encoding applied):  16 kbps
• Coding:  Convolution Coding, Rate = ½ ; Constraint Length = 7, non-inverted G2
• PCM Data Encoding:  Bi-Phase-L (Manchester)
• Symmetry of PCM Bi-Phase Waveform:  Mark-to-Space Ratio between 0.98 and 1.02
• Necessary Bandwidth:  64 kHz

The RF transmitter will be required to tolerate environments of launch, 2.5 years of deep space cruise, Entry, Descent, and Landing, and a storage period of approximately one year on the Martian surface. Note that the RF transmitter will be in an unpowered state for a majority of the cruise except for short durations during health check-outs. For planning purposes, this requirement will involve the design, development, manufacture, testing, qualification, and delivery to NASA/MSFC of multiple RF transmitter units.  Due to the design configuration of the MAV, mass (minimal) is a key factor in determining the selected RF transmitter.

Organizations interested in supporting development of the RF transmitters should contact MSFC no later than Nov. 16.