SOLRAD (short for "SOLar RADiation," sometimes presented as "SOLRAD") was an American series of

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

s sponsored by the

US Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

in a program to continuously monitor the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

. SOLRAD was the

Naval Research Laboratory The United States Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and the United States Marine Corps. Located in Washington, DC, it was founded in 1923 and conducts basic scientific research, appl ...

's first post-

Vanguard The vanguard (sometimes abbreviated to van and also called the advance guard) is the leading part of an advancing military formation. It has a number of functions, including seeking out the enemy and securing ground in advance of the main force. ...

satellite. SOLRAD-GRAB_intelligence_satellite_-_Smithsonian_Air_and_Space_Museum_-_2012-05-15

Background

Until the Kennedy administration, American satellite launches were unclassified. As a result, the

United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...

and the Navy found themselves in the awkward position of wanting to orbit spy satellites but not reveal their nature to potential enemies. Just as the Air Force elected to pair their capsule film recovery satellites with biological payloads under the Discoverer program, so did the Navy develop a scientific cover for its GRAB series of radio/radar surveillance (

ELINT Signals intelligence (SIGINT) is the act and field of intelligence-gathering by interception of ''signals'', whether communications between people (communications intelligence—abbreviated to COMINT) or from electronic signals not directly u ...

) satellites. The field of solar X-ray astronomy lent itself well to such an application. As the Earth's atmosphere absorbs extraterrestrial X-ray sources (of which the Sun is by far the most prominent), it is necessary to send sensors high in or above the atmosphere to detect them. Otherwise, a vast spectrum of solar output is unavailable to Earthbound scientists. Thus, the GRAB satellites would be equipped with X-ray sensors such that they could conduct publicly available scientific research while secretly spying on other countries' military installations. Moreover, through continuous observation of the Sun, the SOLRAD satellites would help the military better understand the effect of solar activity (including

solar flares A solar flare is a relatively intense, localized emission of electromagnetic radiation in the Stellar atmosphere, Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar partic ...

) on radio communications.

Development

When the

National Aeronautics and Space Administration The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the United States's civil space program, aeronautics research and space research. Established in 1958, it su ...

was established on July 29, 1958, most of the NRL Vanguard group's 200 scientists and engineers became the core of NASA's spaceflight activities (though the group remained housed at NRL until the new facilities at the

Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C., in Greenbelt, Maryland, United States. Established on May 1, 1959, as NASA's first space flight center, GSFC ...

in Beltsville, Md. became available in September 1960). Despite this exodus, NRL satellite and space-based research continued. Through the advocacy of NRL engineer Martin Votaw, a small contingent of remaining NRL rocket scientists and technicians regrouped to form the Satellite Techniques Branch headed by Votaw. Their first project was SOLRAD. The new branch was tasked with creating the engineering hardware of the "satellite bus," responsible for the structure, power supply, command, telemetry and the coordination of a satellite, along with its interface with the booster. The branch also handled any special circuitry needed to support the satellite payload. The SOLRADs were not a standardized series of satellites. The first five SOLRADs, launched 1960–1962, were scientific payloads aboard GRAB

satellites, whose primary mission was to monitor foreign radar and communications systems. Starting in 1963, the next three SOLRADs were stand-alone satellites co-launched with next-generation

POPPY A poppy is a flowering plant in the subfamily Papaveroideae of the family Papaveraceae. Poppies are herbaceous plants, often grown for their colourful flowers. One species of poppy, '' Papaver somniferum'', is the source of the narcotic drug ...

surveillance satellites, and beginning with SOLRAD 8, in 1965, SOLRADs were launched alone under the auspices of the Explorer program.

Launches

{, class="wikitable" ! Name ! Launch date ! International Designators ! Other names ! Launch vehicle , - , SOLRAD mass simulator , 13 April 1960
1960-003C
, – , Thor DM-21 Ablestar , - , SOLRAD 1 , 22 June 1960
1960-007B
, GRAB-1 , Thor DM-21 Ablestar , - , SOLRAD 2 , 30 November 1960 (failed launch)
SRD-2
, GRAB-2 , Thor DM-21 Ablestar , - ,

SOLRAD 3 SOLRAD (SOLar RADiation) 3 was a X-ray astronomy#Stellar X-ray astronomy, solar X-ray satellite, the third in the SOLRAD program. Developed by the United States Navy's United States Naval Research Laboratory, Naval Research Laboratory (USNRL), ...

, 29 June 1961
1961-015B
, GRAB-3a, Injun 1 , Thor DM-21 Ablestar , - , SOLRAD 4 , 24 January 1962 (failed launch) , , GRAB, Injun 2 , Thor DM-21 Ablestar , - , SOLRAD 4B , 26 April 1962 (failed launch)
SRAD4B
, GRAB-3b ,

Scout X-2 Scout X-2 was an American expendable launch system and sounding rocket which was flown twice in 1962. It was a four-stage rocket, based on the earlier Scout X-1, uprated first and third stages. It was a member of the Scout (rocket family), Scout f ...

, - , SOLRAD 5 , Not launched , – , GRAB , – , - , SOLRAD 6 , 15 June 1963
1963-021C
, Solrad 6A , Thor-Agena D , - , SOLRAD 7A , 11 January 1964
1964-001D
, Solrad 6{{cite journal, url=http://esoads.eso.org/abs/1968SoPh....5..546L, title=The 44 60 Å flux during the ascending period of the solar cycle no. 20 (1964 67) , bibcode=1968SoPh....5..546L , access-date=January 10, 2019, last1=Landini , first1=M. , last2=Fossi , first2=B. C. Monsignori , last3=Poletto , first3=G. , last4=Tagliaferri , first4=G. L. , journal=Solar Physics , year=1968 , volume=5 , issue=4 , page=546 , doi=10.1007/BF00147019 , s2cid=120525776 , url-access=subscription , Thor Augmented Delta-Agena D , - , SOLRAD 7B , 9 March 1965
1965-016D
, – , Thor Augmented Delta-Agena D , - , SOLRAD 8 , 19 November 1965
1965-093A
, Explorer 30 ,

Scout X-4 Scout may refer to: Youth movement *Scout (Scouting), a child, usually 10–18 years of age, participating in the worldwide Scouting movement **Scouts (The Scout Association), section for 10-14 year olds in the United Kingdom **Scouts BSA, sectio ...

, - , SOLRAD 9 , 5 March 1968
1968-017A
, Explorer 37 , Scout B-1 S160C , - , SOLRAD 10 , 9 July 1971
1971-058A
, Explorer 44 ,

Scout B The Scout family of rockets were American launch vehicles designed to place small satellites into orbit around the Earth. The Scout multistage rocket was the first orbital launch vehicle to be entirely composed of solid fuel stages. It was also t ...

S177C , - , SOLRAD 11A , 14 March 1976
1976-023C
, ,

Titan IIIC The Titan IIIC was an expendable launch system used by the United States Air Force from 1965 until 1982. It was the first Titan (rocket family), Titan booster to feature large solid rocket motors and was planned to be used as a launcher for the D ...

, - , SOLRAD 11B , 14 March 1976
1976-023D
, ,

, - , SOLRAD 11C , Not launched
SRD-11C
, , –

References

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