Orbiting Vehicle
Orbiting Vehicle or OV, originally designated SATAR, comprised five different series of standardized American satellites operated by the US Air Force, launched between 1965 and 1971. Forty seven satellites were built, of which forty three were launched and thirty seven reached orbit. With the exception of the OV3 series and OV4-3, they were launched as secondary payloads, using excess space on other missions. This resulted in extremely low launch costs and short proposal-to-orbit times. Typically, OV satellites carried scientific and/or technological experiments, 184 being successfully orbited through the lifespan of the program. A common research focus was assessing the hazards of the near Earth environment to astronauts and equipment.
The first OV series, designated OV1, was built by General Dynamics and carried on suborbital Atlas missile tests; the satellites subsequently placed themselves into orbit by means of an Altair-2 kick motor. The three Northrop-built OV2 satellites were built using parts left over following the cancellation of the Advanced Research Environmental Test Satellite and flew on Titan IIIC test flights. Space General built the OV3 satellites, the only series to be launched on dedicated rockets; six were launched on Scout-B rockets between 1966 and 1967. OV4 satellites were launched as part of a test flight for the Manned Orbiting Laboratory, with two satellites conducting a communications experiment whilst a third, OV4-3, was the primary payload, a boilerplate mockup of the MOL space station. Two further OV4 satellites, duplicates of the first two, were built but not launched. OV5 satellites were launched as secondary payloads on Titan IIIC rockets as part of the Environmental Research Satellite program.
The OV program was phased out in the late 1960s, succeeded by the Space Test Program, which focused on tailored satellites with specific payloads rather than standardized ones. The last of the series flew in 1971.
Program origin and operations
The Orbiting Vehicle satellite program arose from a US Air Force initiative, begun in the early 1960s, to reduce the expense of space research. Through this initiative, satellites would be standardized to improve reliability and cost-efficiency, and where possible, they would fly on test vehicles and/or piggybacked on other satellite launches. In 1961, the Air Force Office of Aerospace Research created the Aerospace Research Support Program to request satellite research proposals and choose mission experiments. The USAF Space and Missiles Organization created their own analog of the ARSP called the Space Experiments Support Program, which sponsored a greater proportion of technological experiments than the ARSP.In 1966, the OAR annual budget was only about, which was notably low. This was partly possible due to the satellites being launched as secondary payloads on rocket test flights. Since these were necessarily of lower reliability than launches on seasons rockets, this meant the failure rate was higher: of the five OV missions launched in 1965, only one was successful. As each rocket launched to a unique orbit, failure to loft a satellite on a given launch meant the loss of data to be gained on that particular course. Experiments built for a certain flight, designed for their rocket's orbit, often had no back-up.
Experiments to be flown on the OV satellites were proposed by various laboratories in pursuit of their current research projects. These ranged in size from small black boxes to complete satellites. Each lab supported the building and testing of experiments as well as analysis of data returned from them. OAR prioritized the experiments on their scientific or engineering merit and also their feasibility; after picking the experiments, OAR then modified their choices based on funding available and managerial oversight. These final choices were passed by Air Force Headquarters and the Department of Defense—NASA was also consulted to ensure they were not launching flights to acquire the same data. OAR selected 22 experiments for satellite flights in 1966 and 30 for 1967.
Implementation of the OV program, as well as procurement of the launching rockets, was generally carried out by the Los Angeles OAR office, commanded by Lt. Col. John C. Hill, and sited at Air Force Space Systems Division Headquarters in Los Angeles. Integration of the rocket and satellite was managed by SSD and the Air Force Ballistic Systems Division.
Summary of Orbiting Vehicle programs
Five distinct OV series of standardized satellites were developed under the auspices of these agencies.| Series | Contractor | First launch | Last launch | Built | Launched | Failed to orbit |
| OV1 | General Dynamics | 1965-01-21 | 1971-08-07 | 23 | 23 | 4 |
| OV2 | Northrop | 1965-10-15 | 1968-09-26 | 5 | 3 | 0 |
| OV3 | Space General AFRCL | 1967-04-22 | 1967-12-04 | 6 | 6 | 1 |
| OV4 | US Air Force Martin Marietta | 1966-11-03 | 1966-11-03 | 5 | 3 | 0 |
| OV5 | TRW Systems AFRCL Northrop | 1967-04-28 | 1969-05-23 | 9 | 8 | 1 |
OV1
Background
The OV1 series was an evolution of the 2.7 m "Scientific Passenger Pods", which, starting on 2 October 1961, were affixed to suborbital Atlas missile tests and conducted scientific experiments during their short time in space. General Dynamics received a $2 million contract on 13 September 1963 to build a new version of the SPP that would carry a self-orbiting satellite. Once the Atlas missile and ARS reached apogee, the satellite inside would be deployed and thrust itself into orbit. In addition to the orbital SPP, General Dynamics would create six of these satellites, each to be long with a diameter of, able to carry a payload into a circular orbit.Dubbed "Satellite for Aerospace Research", the series of satellites was originally to be launched from the Eastern Test Range on Atlas missions testing experimental Advanced Ballistic Re-Entry System nosecones. However, in 1964, the Air Force transferred ABRES launches to the Western Test Range causing a year's delay for the program. Moreover, because WTR launches would be into polar orbit as opposed to the low-inclination orbits typical of ETR launches, less mass could be lofted into orbit using the same thrust, and the mass of the SATAR satellites had to be reduced.
After OV1-1, the last ABRES test launch, OV1-2 through 12 were launched on decommissioned Atlas D ICBMs, with the exception of OV1-6, launched via the Titan IIIC tasked for the Manned Orbiting Laboratory test flight. The OV1 series from OV1-13 onward were launched on decommissioned Atlas Fs.
Spacecraft
The standard OV1 satellite, long and in diameter, consisted of a cylindrical experiment housing capped with flattened cones on both ends containing 5000 solar cells producing 22 watts of power. Two antennae for transmitting telemetry and receiving commands extended from the sides of the spacecraft. 12 helium-pressurized hydrogen peroxide thrusters provided attitude control. Starting with OV1-7, the solar cells were flat rather than rounded, and the satellites carried the Vertistat attitude system that used a Sun sensor to determine the spacecraft's orientation to the Sun. OV1-13 and OV1-14 were the first in the OV1 series to use pulse-code modulation digital telemetry, which afforded the return of more and more precise data from the satellites.Operations
Ultimately, only the first of the SATARs, ever flew piggyback on an ABRES mission. The rest were flown on ex-ICBM Atlas D and F boosters specifically purchased by the OAR for the OV1 series. The early Atlas D's were launched from "coffin" silos, and their aiming point was typically the island of Guam. The satellites were mounted in the nose cone of the launching rocket; OV1-1, OV1-3 and OV1-86 were side mounted. A jettisonable propulsion module with an Altair-2 solid-propellant motor provided the thrust for final orbital insertion.The OV1/Atlas combination was economical for the time, costing just per launch. By flying as many as three satellite pods on a single rockets, payload costs were brought down significantly. The standardized format also afforded a quick experiment proposal-to-launch period of just fifteen months. The OV-1 program was managed by Lt. Col. Clyde Northcott, Jr.
Significant results
Data from OV1-4's Tissue Equivalent Ionization Chamber, calibrated against a similar instrument orbited on Gemini 4, determined the radiation dose Gemini astronauts traveling at OV1-4's altitude would receive: 4 rads per day at a 30° inclination orbit or 1.5 rads per day at a 90° inclination orbit.In late May 1967, during a period of high solar and magnetic activity, OV1-9 returned the first evidence of Earth's long theorized but never measured electric field. The satellite detected a stream of protons flowing out of the atmosphere into space moving at more than per second. OV1-9 also studied the variation of proton fluxes in the outer Van Allen Belt during that same period, determining that fluxes were ten times greater four days after May's maximum solar activity than they had been before the flare; it took ten days for the fluxes to return to normal levels. The X-ray spectrometer on the co-launched OV1-10 returned the most comprehensive set of solar X-ray observations to date. These data enabled scientists to determine the relative density of neon to magnesium in the solar corona through direct observation rather than using complicated mathematical models. The ratio of neon to magnesium was found to be 1.47 to 1.
OV1-13, launched 6 April 1968, measured increases in energy and intensity of electrons during a geomagnetic storm that took place 10 June 1968. OV1-13 data also clarified how the particle flow caused by solar storms created these high altitude increases.
Data returned by OV1s 15 and 16 returned the first substantial set of data on the density of Earth's atmosphere between the altitudes of and and proved that increased solar activity increased the air density at high altitudes, contradicting the prevailing model of the time. Moreover, the satellites determined that the density of the upper atmosphere was 10% lower than predicted by theoretical models. OV1-15/16 data led to improved atmospheric models that allowed the Air Force to better predict where and when satellites would decay and reenter.
From 1966-69, gravity-gradient stabilization was tested in low Earth orbit on several satellites of the [|United States Air Force's OV-1 series] with a system called Vertistat. Consisting of three -long horizontal booms forming a 'y' and two -long vertical booms, Vertistat was used unsuccessfully on OV1-7, OV1-86, and OV1-17, but successfully on OV1-10.