Transit-O (NNS, Oscar)

Transit-O [USN]

The Transit-O series of satellites that closely followed the design of Transit 5C-1 were called “Oscars” (Oscar is the phonetic alphabet for “O”, i.e., operational) and had one important change: Hysteresis rods were installed on the solar panels to dampen the residual motion after the satellite despin operation in orbit following launch).

The original plan was for the Oscar satellites to be built by the Naval Avionics Facility at Indianapolis (NAFI), and NAFI did build Oscars 1, 2, 3, 5, and 7. All except Oscar 3 reached orbit. However, the fabrication of the satellites did not meet specifications, and those that achieved orbit operated only a few weeks. After Oscars 1 and 2 failed to operate more than a few days, the Navy sponsor decided that APL would refurbish the subsystems built by NAFI for Oscars 4, 6, 8, 9, and 10, and then assemble and launch them. These satellites worked for 7 to 11 months in orbit. APL built Oscars 11 through 17 while the Navy sought a production contractor. Ultimately, RCA was selected and produced all satellites beginning with Oscar 18. The failures of Oscars 4, 6, 8, and 9 were due to several factors considered to be workmanship-related. For Oscar 10, a decrease in the number of solar cells available for charging the batteries was caused by thermal working of the solar cell interconnections as the satellite passed through the Sun and shade while orbiting the Earth. The problem was fixed on Oscar 12, which was the next operational satellite launched. Oscar 11 was not used at this time. It was later modified and launched as the satellite designated TRANSAT to perform related experiments. Beginning with Oscar 12, the satellites demonstrated an average orbital lifetime of more than 14 years. Two satellites, Oscars 13 and 20, operated for more than 20 years. Oscar 17 provides an interesting side note in the history of Transit. The satellite was turned over to the National Air and Space Museum in 1976 and was displayed to the public for more than 8 years. In 1984, it was refurbished at APL and launched as the Polar Bear (Polar Beacon Experiment and Auroral Research satellite) to collect data for studying communications over the Earth's polar regions. When the Navy contracted with RCA to build the Oscars, the satellite lifetimes were expected to be about 14 months. After RCA built Oscars 18 through 32, it became clear that the orbital lifetimes were much longer than anticipated so satellite production ceased. All unlaunched satellites were placed in containers for long-term storage at RCA. The row of gray containers became known as “the long gray line.”

By the late 1980s, the Scout-G1 rocket was able to launch about 260 lb into Transit's operational orbit. After a feasibility investigation by APL, the Navy awarded RCA a contract to launch two Oscar satellites on the same launch vehicle. This dual-launch method was called "stacked Oscars on Scout" (SOOS). This method alowed the remaining Transits to be stored in space and to be activated when needed.

Transit was superseded by the GPS global positioning system. The use of the satellites for navigation was discontinued at the end of 1996 but the satellites continued transmitting and became the Navy Ionospheric Monitoring System (NIMS).