(99K)Relay I was launched on December 13, 1962 into an elliptical orbit with an apogee of 4012 nmi. which took it through the Earth's inner radiation belt. This orbit allowed Relay to measure the radiation in the belt and to study its effects on satellite electronics. Many lessons in communications spacecraft design were learned from the project. The idea of flying experimental communications spacecraft is to try new things and see if they do or don't work. Failures are to be expected and provide the learning experience needed for technology advancement.
Relay I experienced a failure in its primary transponder's power supply and had to switch to its backup transponder which performed well.
A problem that plagued Relay I was spurious commands. The command receiver was continuously on and the antennas were shared with the telemetry transmitter. The command word was only 6 bits long. The most common anomalies were words 101010 and 010101. Relay I recorded 401 anomalies during its first year (anomalies were observed when the satellite was in view of the ground stations, which was only 15% of its orbit). Interference from the wideband subsystem was the main culprit, so a filter was added to the transmission line of the command receiver in Relay II to alleviate the problem. Relay II also had improved circuits that could better differentiate between noise and command signals. Relay II only recorded 62 command anomalies.
The charge controller for one of three battery packs failed after about three months. Another problem was a delay during warmup of the transmitter due to TWT lock- up. This affected the usable pass time. With the altitude of Relay I's orbit, it was only in view of a particular ground station for about a half-hour. The normal 3 minute warm- up took as long as 16 minutes when the TWT locked-up.
Relay II, launched on January 21, 1964, was modified to increase its radiation resistance as well as to improve reliability. N/P solar cells were used instead of P/N cells which reduced degradation due to radiation.
Relay I was a little over four feet long and weighed around 172 pounds. Relay II was slightly heavier. The spacecraft was spin stabilized at 150 rpm (around 170 rpm for Relay II) and used magnetic torquers for attitude control. Forty- five Watts of electrical power was supplied from body-mounted solar cells with nicad batteries for storage. Although Relay I had a 1 year design life, its turn-off switch failed so it continued to operate for a second year causing some interference. The communications payload used the spool-shaped (biconical horn) antennas mounted on the mast. The four whip antennas at the other end of the spacecraft were for telemetry, tracking, and command (TT&C).
The payload was redundant in that Relay had a primary transponder and an identical backup. The 10 W output transponders were all solid-state except for the TWT. The satellite received wideband signals from the ground at a frequency of 1725 MHz and transmitted them back to the ground at a frequency of 4169.7 MHz. Each one of the redundant transponders had one 25 MHz wideband (capable of carrying 300 voice or one TV signal) and two 2 MHz narrowband (12 two-way voice) channels.
The primary ground stations (the same as used with Bell Labs' Telstar 1 satellite) were located in Maine, England, France, with others in California, New Jersey, Germany, Italy, Brazil, and Japan. Relay was used to transmit television signals between the US and Europe or Japan. The 1964 Olympic games from Tokyo, Japan were relayed from the US to Europe.
The Relay spacecraft were built by RCA Astro-Electronics (based on systems engineering studies by TRW) for NASA's Goddard Space Flight Center (GSFC).