During the late sixties and early seventies the U.S. Air Force launched a series of satellites in what was known as the Orbiting Vehicle (OV) series. The satellites were essentially of a scientific and technology nature and demonstrated the use of a standard platform. The series came in five sub-series.
The Orbiting Vehicle (OV) 1 series was built by Convair (General Dynamics) as a multipurpose spacecraft to be used in conjunction with the Atlas launch vehicle (although it was also used with other launch vehicles). The basic satellite was a cylinder of 1.40 m long and 0.69 m in diameter with a small globe on one or both ends. It included a jettisonable propulsion module with an Altair 2 (X258) solid fuelled motor. Normally the satellite was mounted in the nose cone but in several cases (OV1-1, OV1-3 and OV186) the structure was sidemounted.
The purpose of OV11, which was launched on January 21, 1965, on an Atlas D vehicle, was carried in a sidepod on a test flight of the Atlas Advanced Ballistic Reentry System (Abres), was to study trapped radiation. The 85 kg satellite carried an omnidirectional proton spectrometer, a micrometeorite detector, an infrared/ultraviolet radiometer, an aspect magnetometer, a solar aspect sensor, a radio noise radiometer and an ion density impedance probe.
The satellite was intended to be placed in a 560 x 2400 km orbit, but the separation mechanism failed to release the satellite from the launch vehicle.
OV12 launched on October 5, 1965, had a mass of 88 kg, conducted radiation studies to measure the impact of radiation on humans. It also tested the backtoback launch configuration of the OV1 series but with a single satellite mounted. The payload consisted of proton and electron dosimeters and spectrometers, an Xray detector, a magnetometer, two tissue equivalent ion chambers, and a shielded proton/electron dosimeter.
The 92 kg OV13 payload, which was carried in a side pod, was to evaluate the biological hazards of trapped radiation and carried a tissue equivalent plexiglass human torso which was implanted with an ion chamber, spectrometer and linear energy transfer device.
The launch vehicle exploded after two minutes of flight on May 27, 1965.
On March 30, 1966, an Atlas D launched two satellites simultaneously. OV14 satellite conducted thermal control experiments with wafers of various materials and coatings. It also performed zerogravity experiments on chlorella algea and multicell duck weed and exposed these specimens to alternate 12 hour periods of light and darkness as photo cells measured the cell division of the organisms. The mass of the satellite was 87.5 kg.
The OV15 satellite, which had a mass of 114 kg,m measured the optical background of the Earth as well as the background of space to provide a basis for military surveillance techniques. Called the Background Optical Radiation experiment, it used five optical sensors, of which three pointed to the Earth and two away from the Earth. The sensors operated in the ultraviolet, infrared, and visible bands of the spectrum. In addition, the satellite tested the varistat gravity gradient stabilization system.
The 202 kg OV16 satellite, which was launched on November 3, 1969, on a Titan IIIC along with several other satellites, carried several balloons which were ejected and served as optical targets which were subject to radiometer measurements and ground observations.
The OV17 and OV18 were launched together on an Atlas D on July 14, 1966. OV17 was to investigate the night airglow, the molecular oxygen distribution, solar xrays, cosmic rays, charged particles and electric fields of the upper atmosphere. The instruments carried were a solar Xray monitor, a nightglow photometer, an electric field detector, a charged particle detector and several radio beacons. The 117 kg satellite failed to orbit, as the door of the payload bay of the launch vehicle, which were of the same design as for OV18, did not open quickly enough. It has also been stated the satellite injection motor failed.
The OV18 had a mass of 3.2 kg and consisted of a 9.14 m diameter wire mesh sphere with a balloon inside. The satellite was used for passive communications tests and to demonstrate the feasibility of the erection of an open gird structure in space. Also referred to as PasComSat, the balloon decomposed, as planned, after a few orbits due to the intense solar ultraviolet radiation.
A number of radiation experiments were carried on OV19, that was launched on December 11, 1966, including an electrostatic analyzer for the study of electrons and protons, a magnetic analyzer, and scintillation spectrometer for electrons, two solid state spectrometers and range energy spectrometer for the measurement of protons, a low-frequency antenna and amplifier to study exospheric radiation, plus three tissue-equivalent ion chambers to determine the space radiation hazard to man.
The same launch also carried OV110, which conducted further studies of space radiation with an all-sky Lyman-alpha photometer to measure hydrogen radiation, a scanning monochromator for ultraviolet day-glow photometry, a monochromator and Geiger-Mueller counters for day-glow photometry, a crystal spectrometer to measure solar X-rays, a heavy primary cosmic ray telescope and a dual rubidium vapor magnetometer.
OV111, which was launched on July 27, 1967, was equipped with eight experiments to measure solar emissions, altitude distribution of atmospheric oxygen and ozone, and charged particles. The instruments included a solar X-ray spectrometer and monitor, a plasma wave detector, a night-glow probe, an ultraviolet radiance spectrometer and instruments to measure electron and proton flux. The satellite failed to separate from the launch vehicle.
The same launch vehicle also carrier the OV186 which consisted of a satellite similar to the OV18, mated with a propulsion module as used on OV16. The objective of the flight was to measure the change over time in energy of cosmic rays, as well as the isotrophy of those rays. It was also to determine the emission properties of the Earths oxygen mantle and to determine the radiometric temperature of the Earths atmosphere. The instruments carried consisted of a cosmic ray telescope, a 60GC radiometer, a 114B interferometer and a WW4 radiometer. As the 105 kg satellite tumbled, only partial data was gathered.
Finally, the launch on July 27, 1967, placed the 140 kg OV112 satellite in orbit. It made biophysical and physical measurements of the space environment during solar flare activity as part of an overall programme to assess the effect of space radiation on humans. The experiments, which were collectively known as WL701 Flare Activated Radiobiological Observatory (FARO), were a Tissue Equilibrium Ion Chamber, a Linear Energy Transfer Spectrometer, a 20 to 40 MeV Proton Detector, a 45 to 110 MeV Proton Detector, a 3.5 to 5.0 MeV Electron Spectrometer, a Solar Flare Detector, a X-Ray Scintillator, a Solid State Radiation Monitor, a High Energy Particle Detector, a Dose Spectrometer and an Omnidirectional Proton/Electron Spectrometer.
An Atlas F placed the OV113 and OV114 satellites in orbit on 6 April 1968.
The 107 kg OV113 was to measure radiation at altitudes below 8000 km, evaluate the space environments effects on bearings and on friction between various material combinations as well as evaluate flexible cadmium sulphide solar cells. The payload consisted of a GeigerMueller counter, four spectrometers, a magnetic analyser, an electrostatic analyser, various material combinations for the friction and wear experiment and experimental cadmium sulphide solar cells.
The 100 kg OV114 was to measure solar Lymanalpha radiation and VLF and LF radiation in the Van Allen belts. The payload consisted of particle detectors to measure proton fluxes, proton spectra, electron spectra and the time dependence of particles dE/dX telescopes and a Lymanalpha experiment. Due to a power failure the satellite ceased transmitting data after one week in service.
OV115 was launched on July 11, 1968, to identify the cause of large and sudden fluctuations encountered in satellite trajectories, with the ultimate goal of being able to predict these fluctuations and their magnitude. The satellite investigated the upper atmosphere with an array of instruments, which included a microphone density gauge, ion gauges, mass spectrometers, energetic particle detectors, solar X-ray and ultraviolet flux monitors, an ionosphere monitor and a triaxial accelerometer. In addition ground based measurements were made. The satellite was also known as Solar Perturbation of Atmospheric Density Experiment (Spades).
The same Atlas F launch vehicle also carried OV116, which measured the time and space variations of atmospheric density at altitudes as low as 120 km. Also referred to as Cannonball1 or Low Altitude Density Satellite (Loads)1, the satellite was a brass sphere with a diameter of 58 cm and a mass of 272 kg giving it a density equal to 690.5 kg/cubic meter, required to ensure the satellite would not immediately decay. It carried a triaxial accelerometer.
On March 18, 1969, an Atlas F placed four OV1 series satellites into orbit. OV117 measured the incoming solar electromagnetic radiation and the interaction of this radiation with the Earths outer atmosphere. The 12 experiments measured the horizon day-glow and night-glow, solar x-rays, particles, electric fields, and extreme low-frequency propagation. It also tested cadmium-sulphide solar cells and thermal coatings. The satellite, which had a mass of 142 kg, was not correctly stabilzsed and spinned, resulting in four experiments that required proper stabilization returning useless data. The combined payloads on this flight have also been referred to as P69-1.
OV117A, also known as Orbis Cal2, studied the unusual transmission of radiowaves through the ionosphere by monitoring the satellite with several ground stations. The 221 kg satellite consisted of the propulsion module of OV117 which was fitted with two radio beacons operating at 8.98 and 13.25 MHz. The OV118 studied the ionosphere as it affects radiowave propagation. The payload consisted of 16 instruments to measure radio interference, electric fields, horizontal ion density gradients and gamma rays. The gravity gradient booms did not deploy and the satellite, which had a mass of 125 kg, was unstable giving meaningless data. The final satellite on this launch, OV119, made detailed studies of the events causing and sustaining the trapped radiation in the Van Allen belts and studied the hazards to a human of incoming and trapped radiation. It carried seven instruments to study the trapped radiation and five instruments to study radiation hazards. The satellites mass was 124 kg.
The final two satellites in the OV1 series were launched by an Atlas F on August 7, 1971. OV120 and OV121 carried experiments to investigate the properties of the near-Earth environment. The first satellite ejected a further satellite known as OAR-901, Low Altitude Density Satellite II, or Cannonball-2. This was a brass sphere which made air density measurements in the fringes of the Earths atmosphere. OV120 itself carried an energetic proton analyzer to measure the spatial energy dependency of trapped proton flux, as well as a particle and flux thermal detector to measure the electron density and temperature in the upper atmosphere.
OV121 was equipped with an experiment to determine the non-linear impedance and non-linear plasma effects of a long electric dipole antenna, an experiment to measure the atomic oxygen density and the variations in this density during geomagnetic activity as well as an instrument to measure the solar flux and atmospheric composition. Furthermore the satellite released six sub-satellites: the Radar Tracking Density Satellite, OAR-907 or Musketball, which carried a C-band transponder to make air density measurements in the fringes of the Earths atmosphere; a 112 cm diameter rigid sphere (AVL-802 or Rigid Sphere-2); three inflatable spheres with a diameter of 213 cm (identified as Grid Sphere1 and 2 and Mylar Balloon), which were used to determine the ballistic coefficient of spheres and measure the change in this coefficient with the changing altitude; and the Lincoln Calibration Sphere (LCS)4, a radar calibration satellite also known as Rigid Sphere1.
In their day, the Orbiting Vehicle series of satellites were remarkable in that details of the experiments were published, unlike other US Air Force satellites which were classified and remain so in most instances today. We will probably never know the extent to which these small satellites were associated with the classified programs. In a future issue of MilsatMagazine, Jos Heyman will continue the OV satellite series.