Stanford University

Mars Relay Flight Test Home Page

The crew members toasted the successful completion of the test with (appropriately enough!) French champagne. It didn't seem to matter to any of them that the Sun had yet to rise. Shown in the photo above are Mike Cousins of SRI International, Eric Peragin of CNES, Joe Twicken and Ivan Linscott from Stanford University, John Callas of JPL, and Andre Ribes of CNES.

The test has concluded!!! The final day was dedicated to data uplink and MOC readouts to determine the bit-error performance of the Relay system. Andre and Eric have informed us after analyzing the files received from the MOC readouts that data was transmitted from Stanford and received by the MGS Relay system without any errors at 8 kbps with frequency F1 and at 128 kbps with frequency F2. At 128 kbps with frequency F1, the MGS Relay failed to lock up on the first few frames of the transmission. After that, all was well. The high rate transmissions were successful with transmitted power levels down to 7.6 kiloWatts and the low rate transmissions were successful with levels down to 1.2 kiloWatts.

We have heard that many amateurs around the world have successfully detected the MR beacon. Congratulations!!!

Mode 1 RC1 Mesh

This 3D plot was generated from 40 consecutive spectra which were acquired at the time that the Relay was transmitting in its mode 1 RC1 state. The Stanford receiver was configured at the time so that the Relay beacon appeared at 4 kHz in our passband. The plot graphically illustrates the transmit cycle in which the beacon is in the CW condition for 2 seconds followed by modulated condition for 14 seconds. More than three cycles are shown in the figure. The second harmonics of the RC1 subcarriers are also clearly visible in the figure. Note that these subcarriers go off when the beacon is transmitting CW. The time axis units are seconds. The frequency axis units are kiloHertz. The power axis is linear and not logarithmic (dB).

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Check out some crew photos as well:

Welcome to the home page for the Mars Relay Flight Test at Stanford University. Currently scheduled for the period of November 24-26, 1996, the test involves the transmission of UHF radio signals to the Mars Relay system aboard the Mars Global Surveyor (MGS) spacecraft, and the reception of UHF radio signals from that same radio system. The Mars Relay system was launched aboard the MGS on November 7, 1996, with the purpose of acquiring and relaying the data gathered by landers and penetrators on the Martian surface which were to have been delivered there by the ill-fated Russian Mars 96 spacecraft. Sadly, that spacecraft failed to boost out of Earth orbit and was subsequently lost on November 17, 1996, in the Pacific Ocean west of Chile. The Mars Relay system will also support instruments and micro-probes which will be launched to Mars aboard the Mars Surveyor 98 spacecraft, however, and the Mars Relay Flight Test is still scheduled.

Mars Relay Radio System

On the first day of the test, the Mars Relay beacon will transmit a CW signal to Earth at a UHF radio frequency of 437.1 MHz. At that time, the MGS spacecraft will be approximately 5 million kilometers from Earth on the early part of its voyage to Mars. The signal will be received at Stanford and also by amateur radio operators around the world. The global reception of the Relay signal will help to characterize the gain pattern of the Mars Relay antenna as the MGS spacecraft performs its 100-minute cruise spin.

On the following two days of the test, a UHF signal with up to 10 kW of power will be uplinked to the MGS from Stanford, and the Relay system will receive that signal and then respond with one of its own. The uplink and downlink signals in this portion of the test will be encoded with pseudo-random noise. The two Mars Relay uplink frequencies are 401.5 and 405.6 MHz. The downlink frequency is 437.1 MHz. The downlink signals will again be received at Stanford and by amateur radio operators who are in view of the spacecraft at the same time that Stanford is in view. The encoded downlink signals are significantly weaker than the CW beacon, and it will be a mighty challenge to detect them. An up-to-date test timeline is available. Detailed information about the test can be found on the Mars Relay Flight Test home page at JPL.

SRI/Stanford University 150-foot Dish

The uplink and downlink signals will be transmitted and received with the 150-foot parabolic reflector at Stanford University. Affectionately known as The Dish on the Stanford campus and a common sight to residents of the Silicon Valley, this antenna has a long and storied history. Some of this history as well as technical specifications for this antenna are available here. Currently, the Dish is operated and maintained by SRI International and is shared cooperatively with members of the Space, Telecommunications, and Radioscience Laboratory (STAR Lab) at Stanford University. For the Mars Relay Flight Test, the feed for the 150-foot reflector will be a diagonal horn situated at the prime focus of the antenna. The horn was constructed at SRI specifically for the Relay test by Michael Cousins of SRI. The front-end of the receiver is liquid-cooled and the overall noise temperature (system plus sky) during the test is expected to be on the order of 50-60 K. Managing the test at the SRI/Stanford field site will be Ivan Linscott of the Stanford STAR Lab and Michael Cousins of SRI International.

While the test is underway, accumulated power spectra of the Mars Relay signal as received and processed at Stanford will be available on-line for your viewing pleasure in "near" real-time. The spectra will be produced by a Pentium PC system with a Spectrum TMSC40-based DSP card. In-phase and quadrature samples of the Relay signal will be acquired at speeds up to 125 ksamples/sec (complex) with a resolution of 16 bits for each of the I and Q samples. Accumulated power spectra will be written to disk and plots of the spectra will be displayed in real-time with Matlab. At regular intervals, our spectral display will be written to disk in GIF format and will be transfered to our World Wide Web server. Currently, we plan to update the plot of the Relay power spectra on this Web site every few minutes. Bandwidth limitations of our system and of the Net at large prevent us from doing better. The display will contain the the latest accumulated power spectrum plus a long-term average spectrum.

We will also have have QuickCam photographs from the control room at the 150-foot antenna available on-line in "near" real-time. You may be view those photographs here.

Last updated: 02 December 1996
Joe Twicken