Orbiting Vehicle

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 (OAR) created the Aerospace Research Support Program (ARSP) 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 (SESP), which sponsored a greater proportion of technological experiments than the ARSP.{{Cite magazine |last=Powell |first=Joel W. |last2=Richards |first2=G.R. |date=1987 |title=The Orbiting Vehicle Series of Satellites |url=https://archive.org/details/sim_journal-of-the-british-interplanetary-society_1987-09_40_9/page/417 |url-access=registration |magazine=Journal of the British Interplanetary Society |publisher=British Interplanetary Society |location=London |pages=417–426 |volume=40 |issue=9}}{{rp|417}} Five distinct OV series of standardized satellites were developed under the auspices of these agencies.{{rp|425}}

File:Ov1-1.jpg

The OV1 series was an evolution of the 2.7 m "Scientific Passenger Pods" (SPP), 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 (called the Atlas Retained Structure (ARS)) 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 {{convert|3.66|m|abbr=on}} long with a diameter of {{convert|.762|m|abbr=on}}, able to carry a {{convert|136|kg|abbr=on}} payload into a circular {{convert|805|km|abbr=on}} orbit.

Dubbed "Satellite for Aerospace Research" (SATAR), the series of satellites was originally to be launched from the Eastern Test Range on Atlas missions testing experimental Advanced Ballistic Re-Entry System (ABRES) 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.{{rp|417}}

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.{{rp|418,420-421}}

The standard OV1 satellite, {{convert|1.387|m|abbr=on}} long and {{convert|.69|m|abbr=on}} in diameter, consisted of a cylindrical experiment housing capped with flattened cones on both ends{{cite web|url=https://space.skyrocket.de/doc_sdat/ov1.htm|title=OV1|last=Krebs|first=Gunter|access-date=24 April 2020}} containing 5000 solar cells producing 22 watts of power. Two {{convert|.46|m|abbr=on}} 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.{{rp|418–429}} 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.{{cite magazine|url=https://archive.org/details/1968generaldynamicsnews/page/n61/mode/2up?q=%22ov1-13%22|title=OV1 Satellites Boosted Into Space by Atlas|magazine=1968 General Dynamics News|date=1968|publisher=Convair|page=62}}

File:Lt. Col. Clyde Northcott, Jr., OV1 program manager.jpg

Ultimately, only the first of the SATARs, (OV1-1, called Atmospheric Research Vehicle (ARV) at the time){{cite web|url=https://history.nasa.gov/AAchronologies/1965.pdf|title=Aeronautics and Astronautics, 1965|publisher=NASA|access-date=24 April 2020}}{{rp|24}} 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 (except OV1-6, which flew on the Manned Orbiting Laboratory test flight on 2 November 1966).{{rp|418–422}} Typically, 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 $1.25 million per launch ($4545 per {{convert|1|kg|abbr=on}} of payload). The standardized format also afforded a quick experiment proposal-to-launch period of just fifteen months.{{rp|418}} The program was managed by Lt. Col. Clyde Northcott, Jr.{{cite book|title=Proceedings of the OAR Research Applications Conference, 14 March 1967|chapter=The OV1-Promoter of timely space research|publisher=Officer of Aerospace Research, United States Air Force|location=Washington D.C.|date=1967}}

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 (~{{cvt|950|km}}) would receive: 4 rads per day at a 30° inclination orbit or 1.5 rads per day at a 90° (polar) inclination orbit.{{cite book|title=Space Radiation Biology and Related Topics Prepared Under the Direction of the American Institute of Biological Sciences for the Office of Information Services, United States Atomic Energy Commission|editor=Cornelius A. Tobias and Paul Todd|publisher=Academic Press Inc.|page=68|date=1974|isbn=9781483273860|url=https://books.google.com/books?id=GDLLBAAAQBAJ}}

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 {{cvt|60,000|km}} 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.{{cite book|url=https://books.google.com/books?id=4u_fnzEuvVYC&dq=ov1-9&pg=PA169|title=Air Force Cambridge Research Laboratories Report on Research for the period July 1967 — June 1970|page=169|date=December 1970|location=Bedford, MA|publisher=Air Force Systems Command}} 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 (+/- .38).{{cite journal|journal=The Astrophysical Journal|volume=203|page=L139|date=1976|title=The Relative Abundance of Neon and Magnesium in the Solar Corona|author1=H.R. Rugge|author2=A.B.C. Walker, Jr|doi=10.1086/182038|bibcode=1976ApJ...203L.139R|hdl=2060/19760010939|s2cid=92759580 |url=https://ui.adsabs.harvard.edu/link_gateway/1976ApJ...203L.139R/ADS_PDF|hdl-access=free}}

OV1-13, launched 6 April 1968, measured increases in energy and intensity of electrons during a geomagnetic storm that took place 10 June 1968.{{cite report|title=Analysis of Electron Data from the OV1-13 Satellite.|date=25 January 1974|author1=Klumpar, David L.|author2= Webber, William R.|author3=Lockwood, John A.|publisher=NEW HAMPSHIRE UNIV DURHAM DEPT OF PHYSICS}} OV1-13 data also clarified how the particle flow caused by solar storms created these high altitude increases.{{cite report|url=https://books.google.com/books?id=MF2dExiimrsC&dq=%22ov1-13%22&pg=PA125|title=Report on Research at AFCRL for the Period July 1970 - June 1972|date=February 1973|publisher=The Air Force Cambridge Research Laboratories|page=125}}

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 {{cvt|100|km}} and {{cvt|200|km}} and proved that increased solar activity increased the air density at high altitudes, contradicting the prevailing model of the time.{{cite report|title=Densities from Satellites OV1-15 and OV1-16|author1=Kenneth S. W. Champion|author2=F.A. Marcos|url=https://books.google.com/books?id=yxJoXtysBUIC&pg=PP8|pages=iii,1–2, 18|date=23 October 1969|publisher=Air Force Cambridge Research Laboratories}} Moreover, the satellites determined that the density of the upper atmosphere was 10% lower than predicted by theoretical models.{{cite book|title=OAR progress 1969|page=123|chapter=Atmospheric-density accelerometer and low-altitude density satellites (OV1-15 and OV1-16)|author=unknown|date=1969|chapter-url=https://books.google.com/books?id=bRd3e4OTP7AC&dq=ov1-16&pg=PA119}} 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 {{cvt|15.5|m}}-long horizontal booms forming a 'y' and two {{cvt|19|m}}-long vertical booms,{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1969-025A|title=OV1-17|publisher=NASA|access-date=16 July 2024}} Vertistat was used unsuccessfully on OV1-7, OV1-86, and OV1-17, but successfully on OV1-10.

File:OV2-1diagram.jpg

The OV2 series of satellites was originally designed as part of the ARENTS (Advanced Research Environmental Test Satellite) program, intended to obtain supporting data for the Vela satellites, which monitored the Earth for violations of the 1963 Partial Test Ban Treaty. Upon the cancellation of ARENTS due to delays in the Centaur rocket stage, the program's hardware (developed by General Dynamics) was repurposed to fly on the Titan III{{rp|417}}{{rp|422}} (initially the A,{{cite magazine| date = February 8, 1965| title = OV2-1A Readied for Titan 3 A Test| url = http://archive.aviationweek.com/issue/19650208#!&pid=26| magazine = Aviation Week and Space Technology| location = New York| publisher = McGraw Hill Publishing Company| access-date = February 10, 2020|url-access=subscription}} ultimately the C) booster test launches. The USAF contracted Northrop to produce these satellites, with William C. Armstrong of Northrop Space Laboratories serving as the program manager.

The OV2 satellites were all designed on the same plan, roughly cubical structures of aluminum honeycomb, {{convert|.61|m|ft|abbr=on}} in height, and {{convert|.58|m|ft|abbr=on}} wide, with four {{convert|2.3|m|ft|abbr=on}} paddle-like solar panels mounted at the four upper corners, each with 20,160 solar cells. The power system, which included NiCd batteries for night-time operations, provided 63 W of power. Experiments were generally mounted outside the cube while satellite systems, including tape recorder, command receiver, and PAM/FM/FM telemetry system, were installed inside. Four small solid rocket motors spun, one on each paddle, were designed to spin the OV2 satellites upon reaching orbit, providing gyroscopic stability. Cold-gas jets maintained this stability, receiving information on the satellite's alignment with respect to the Sun via an onboard solar aspect sensor, and with respect to the local magnetic field via two onboard fluxgate magnetometers. A damper kept the satellites from precessing (wobbling around its spin axis). Passive thermal control kept the satellites from overheating.{{rp|422}}

Three OV2 satellites with different mission objectives were originally planned when the OV2 program began. The OV2 series was ultimately expanded to five satellites, all with different goals. Only OV2-5, a radiation and astronomical satellite, achieved a degree of success.{{cite web|url=https://space.skyrocket.de/doc_sdat/ov2.htm|title=OV2|last=Krebs|first=Gunter|publisher=Gunter's Space Page|access-date=February 12, 2019}}

OV2-5 proton energy data collected 2–13 October 1968 in the energy range of 0.060 to 3.3 Mev, showed an eight-fold reduction in particle flux between solar storms and quiet periods. Measuring the angle at which protons encountered the satellite also helped refine theoretical models of how the magnetosphere interacts with the flux of charged particles.{{cite journal|title=Proton energy distributions from 0.060 to 3.3 Mev at 6.6 Earth radii|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA075i028p05373|journal=Journal of Geophysical Research|volume=75|issue=28|page=5373|last1=Stevens|first1=John R.|last2=Martina|first2=E. Frank|last3=White|first3=R. Stephen |date=1 October 1970|doi=10.1029/JA075i028p05373|bibcode=1970JGR....75.5373S|access-date=8 June 2021}}

File:OV3-2.jpg

Unlike the OV1 and OV2 series satellites, which were designed to use empty payload space on rocket test launches, the six OV3 satellites all had dedicated Scout boosters. In this regard, the OV3 series was more akin to its civilian science program counterparts (e.g. Explorer). OV3 differed from NASA programs in its heavy use of off-the-shelf equipment, which resulted in lower unit cost.

The first four satellites in the series were made the Aerojet subsidiary Space General Corporation under a $1.35m contract awarded 2 December 1964, the first satellite due October 1965. The last two satellites were built by Air Force Cambridge Research Laboratory (AFCRL), which also managed the entire series and provided four of the OV3 payloads.{{rp|422–423}}

Charles H. Reynolds, who worked at AFCRL from 1955, was the technical manager for the OV3 program.{{cite magazine|url=https://play.google.com/books/reader?id=aQtIAQAAIAAJ&hl=en&pg=GBS.RA6-PA10|title=Anniversary of OV3-1|author=Charles H. Reynolds|magazine=research review|publisher=Office of Aerospace Research|volume=6|number=7|pages=10–11|date=July 1967|access-date=1 April 2021}}

The OV3 satellites were octagonal prisms, {{cvt|.74|m}} in length and width (for OV3-5 and OV3-6, length was reduced to {{cvt|.53|m}}), with experiments mounted on booms. 2560 solar cells provided 30 Watts of power. The satellite was spin-stabilized, but because it was asymmetrical once its booms were extended,{{cite book|title=Low-Energy Auroral Electrons Measured by Satellite OV3-1|url=https://books.googleusercontent.com/bookscontent?req=AKW5Qadlmcty2L2tgax2N5z5McqgP0u6hs7jtTRYuV_Mlj_j2G0UZxw7KUAjly5OMjXFeK9-H82Q_djDtMEpyHbTlU6QZNb0oVHknbCD9pSKtk8QKUwRWzQMvH8LcqZPzWtb4Dn0n3D806pbVHu95hXqF6vjCCfDhxV05_BxJf5PHns6tBq1FGmc9Ya3HvCWGmrxIBsH-rj3tqrUiOiynUdgn1Fhp5jxVqSf75msQ5LS-Mp3ZH7itzg--ukr62kiCB9nFlHJSeI3GIvWqi2N0f8p8qTUKYaw|author=George A. Kuck|date=August 1968|access-date=8 June 2021}} OV3-2 maintained its attitude in orbit with a precession damper.{{rp|422–423}} The spacecraft was spin stabilized at 8 revolutions per minute (rpm) A sun sensor, as well as an onboard tri-axial magnetnometer, gave information on the satellite's aspect (facing), its spin rate, and rate of precession.{{cite report|title=Research Review|url=https://books.google.com/books?id=Gz8qAQAAIAAJ&dq=%22research+review%22+%22ov3-2%22&pg=RA1-PA4|pages=4–5|publisher=Office of Aerospace Research|volume=6|number=2|date=February 1967}}{{rp|423}} Design life-span was one year.{{rp|423}}

The OV3 program ultimately comprised 6 missions, five of them successful. The last (OV3-6) flew on 4 December 1967. The OV3 program was terminated following OV3-6 in favor of the cheaper OV1 program.{{rp|423}}

• OV3-1 had a near polar orbit and returned useful data on the energy and distribution of electrons in the auroral regions.
• Data returned by OV3-4 helped prove and refine theoretical models of radiation dosage an astronaut would receive at orbital altitudes.
• OV3-3 VLF receiver data determined the location of the plasmapause (the outer boundary of the Earth's inner magnetosphere).{{cite journal|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA077i010p01802|journal=Journal of Geophysical Research|title=Observations of SAR arcs from OV1-10|author1=S. R. LaValle|author2=D. D. Elliott|date=1 April 1972|volume=77|issue=10|pages=1802–1809|doi=10.1029/JA077i010p01802|bibcode=1972JGR....77.1802L}}
• OV3-2 observed ambient charged particle variations before, during, and after the 12 November 1966 South American solar eclipse.{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-097A|title=OV3-2|publisher=NASA|access-date=27 September 2021}} OV3-2 also conducted ionospheric and aurora research in orbit in conjunction with AFCRL KC-135 aircraft flying underneath, conducting simultaneous measurements.{{cite book|title=Report on Research at AFCRL July 1965-June 1967|page=113|date=November 1967|publisher=The Air Force Cambridge Research Laboratories|location=Bedford, Massachusetts|oclc=316861363}} The National Research Council of Canada also conducted coordinated, simultaneous ionospheric observations.{{cite book|title=AFCRL Space Science Research During 1967 (Annual Report to COSPAR)|editor=A. McIntyre|publisher=Office of Aerospace Research. United States Air Force|location=Bedford, Massachusetts|date=January 1968|oclc=69188216}}
• OV3-6 measured much larger latitude variations than current atmospheric models had expected. A bulge in the neutral density in the summer hemisphere was also discovered. The data obtained was used to construct more accurate atmospheric models, and to correlate physical chemistry reactions to disturbances originating from the sun.{{cite report|url=https://archive.org/details/DTIC_AD0720277/page/n213/mode/2up?q=%22ov3-6%22|title=DTIC AD0720277: Air Force Cambridge Research Laboratories Report on Research|publisher=Defense Technical Information Center|page=210|date=1 December 1970}}

File:Charles H. Reynolds.jpg

File:Titan-3C_MOL-Gemini-B-Test_3_(crop).jpg

The OV4 series was designed to utilize space aboard the Manned Orbiting Laboratory (MOL) test flights. In September 1964, Raytheon was awarded a $220,000 contract to build a one-off pair of satellites, designed by the U.S.A.F. Avionics Laboratory. These two satellites would investigate long range radio propagation in the charged atmosphere of the ionosphere analogous to the whispering gallery transmission of sounds under a physical dome.{{rp|423}} In this way, the OV4-1 pair would evaluate the ionosphere's F layer as method of facilitating HF and VHF transmissions between satellites not in line of sight of each other.

The OV4-1 satellite pair consisted of a transmitting spacecraft and a receiving spacecraft. OV4-1T's transmitter broadcast on three frequencies in the 20-50 MHz range. OV4-1R included receiving equipment and telemetry broadcast equipment. Launched into slightly different {{cvt|300|km}} orbits, the satellites would test whispering gallery communications over a range of distances; OV4-1T included a small rocket motor to maximize orbital separation (180°) from OV4-1R.{{rp|423}}

Both satellites were cylindrical, {{cvt|.43|m}} in diameter, with domed upper ends. Total length was {{cvt|.9|m}}. Silver oxide/zinc batteries provided for a 50-day lifespan.{{rp|423}}

Two sets of OV4 "whispering gallery" satellites were built. OV4-2T and OV4-2R were never flown.{{rp|423}}

OV4-1T and OV4-1R were scheduled for launch on the MOL Heat Shield Qualification flight, with a Titan IIIC rocket. The dummy MOL (a Titan first-stage oxidizer tank) was equipped with a variety of experiments and dubbed OV4-3.{{rp|423–424}} OV1-6 was also mounted on the Titan III. The rocket took off from Cape Canaveral Launch Complex 40 on 3 November 1966 at 13:50:42 UTC.

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File:Ov5-1.jpg

The OV5 program was a continuation of the Environmental Research Satellite (ERS) series developed by Space Technology Laboratories, a subdivision of TRW Inc. These were very small satellites launched pick-a-back with primary payloads since 1962—a natural fit under the Orbiting Vehicle umbrella. The primary innovation over the earlier ERS series was a command receiver, allowing instructions to be sent from the ground, and a Pulse-code modulation digital telemetry system,{{rp|425}} versus the analog transmitters used on prior ERS missions.{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1965-058C|title=ERS 17|publisher=NASA|access-date=2022-06-08}} Like prior ERS, the OV5s were spin-stabilized and heat was passively controlled. All of the OV5 series were built by TRW with the exception of OV5-6, built by AFCRL, and OV5-9, built by Northrop Corporation.{{rp|425}}

File:Ov5-1 internals.jpg

File:Ov5-4 art.jpg

The OV program orbited 184 experiments at extremely low launch costs and with very short proposal-to-orbit times. OV was succeeded by the Space Test Program, managed by the Space Missile Organization's Space Experiments Support Program, which had absorbed the ARSP in 1968. The Space Test Program followed the new trend in satellites, which preferred custom-built one-offs with specific payloads to vehicles built on standardized plans. Several late OV satellites were launched under the auspices of the new program{{rp|421-422, 425–426}}

{{Reflist}}

Category:Satellites orbiting Earth

Category:Military space program of the United States

Category:Satellite series