What is the Mars Relay Flight Test?
The Mars Relay Flight Test will be a test of the UHF relay on board the Mars Global Surveyor (MGS) spacecraft. The test will occur approximately two weeks after launch of while the spacecraft is still in proximity of the Earth. The Mars Relay will be used at Mars for communications between MGS and small stations placed on the surface of Mars by other missions. The Mars Relay uses frequencies of 437.1 MHz for transmission, and 401.5 and 405.6 MHz for reception. Because these frequencies are near the radio amateur bands, Hams will have the opportunity to help out NASA and listen for the Mars Relay beacon transmission at 437.1 MHz. JPL is currently working with Stanford University to develop the uplink (or transmission) portion of the test at frequencies of 401.5 and 405.6 MHz.
How can Amateur Radio Operators Participate?
The broadcast beacon frequency for the Mars Relay is 437.1 MHz
(the signal will be Doppler shifted). Signal strength should such
that amateurs with capable equipment should be able to detect the
beacon signal even at distance of as much as 10 million kilometers.
Amateurs from around the globe will be asked to monitor the signal
and measure its strength as a function of time (the spacecraft
rotates every 100 minutes). This information will help JPL
establish the functionality and performance of the Mars Relay prior
to its use at Mars. Interested amateurs should register and subscribe to the Mars-Net list server.
When is this experiment?
On 1996 November 24, the beacon will be turned
on for approximately three days. The spacecraft will be
between 5 - 6 million km from earth This period is
the time which the amateur radio experiment will be conducted.
The exact time will be announced on the e-mail reflector and
on this page.
After an initial period in the CW mode, the beacon will be
switched to FM with a pure FM signal on one sub-carrier. The
signal level will drop by approximately 14 dB. This will drop
the signal level below the noise level for most amateur radio
Mars Relay Radio System:
When at Mars, the Mars Relay aboard MGS receives Telemetry from balloons or landed Instrument packages (including cameras, atmospheric and meteorology instruments).
Receive Frequency: 401.5275 MHz and 405.625 MHz.
Transmit Frequency: 437.100 MHz.
Transmitter Power: 1.3 Watts
Beacon Modes: FM or CW
Receive Data Rate: 8 to 128 kilobits per second
Link Margin: See the Antenna Margin Table and
the signal level chart
During the Amateur Radio Experiment: The downlink frequency will be 437.100 MHz. This frequency will shift with respect to Doppler effects. The downlink from the Mars Global Surveyor Spacecraft will be transmitted from the Mars Relay's transmitter with a power of 1.3 Watts through an antenna with better than zero dBi of gain. The spacecraft will be rotating with the axis of rotation about 30 degrees off earth point. This means that the downlink signal will increase and decrease with respect to the period of rotation. The rotation period will be approximately 100 minutes. It is estimated that the Mars Relay antenna gain, as seen from the Earth, will be above 0 dBi in gain for at least 30 minutes out of every 100 minute rotation of the spacecraft.
What information would we like from the Amateur Radio Operators?
Provide the Latitude, Longitude, and Elevation of your antenna
Provide a measurement of the signal relative to UTC.
If possible give the reading relative to a standard reading.
Any information about your antenna and receiver system would also
be helpful. (For example, Gain, Noise Figure, Search Bandwidth,
How do I find out more information?
MGS WWW Page: http://mgs-www.jpl.nasa.gov
See QST, January 1996 for an article on the Mars Relay flight test.
E-Mail reflector, "MARS-NET" which will discuss current issues
relating to MGS. Update notices will be sent through the e-mail
Send message to: Listserv@VM.StLawU.EDU
Message: Subscribe MARS-NET Your-Name Your-Call-sign
For Example: Subscribe MARS-NET Robert R. Smith N6JKQ
To submit messages to the MARS-NET reflector, address your e-mail
message to: MARS-NET@VM.StLawU.EDU
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