Early warning satellite

Artist's rendering of a US DSP phase III satellite.

An early warning satellite is a satellite designed to rapidly identify ballistic missile launches and thus enable defensive military action. This type of satellite was developed during the Cold War and later became a component of missile defense systems.

The United States, Russia and China have a constellation of early warning satellites.

Description

Example of the firing sequence of the Minuteman III intercontinental ballistic missile: the propulsion allows detection by an early warning satellite during phases 2, 3 and 4 corresponding to the operation of the 3 stages of the missile (A, B and C). This missile rises to between 100 and 200 km in altitude (diagram not to scale).

Early warning satellites primarily work through the detection of infrared radiation.^[1] For the detection of ICBMs, this is only possible during the initial phases after a launch. The missile emits a large cloud of hot exhaust as it ascends to the desired altitude. After this stage, detection of the missile is difficult. The thrusters are turned off and the missile separates from previous stages, now carried to its target through momentum alone.

The missile - now without hot exhaust behind it - is rendered invisible to the early warning satellite, making the relatively short first phases of an ICBM a crucial moment for detection. Because the window for detection is small, multiple satellites are necessary for complete coverage of Earth.^[2]

In orbit, the satellites are able to detect an ICBM launch through earth's background infrared radiation due to specific properties in how the water vapor absorbs infrared radiation. Once the missile has passed through the water-rich lower layers of the atmosphere, the specific infrared spectrum given off by the exhaust contrasts against the infrared emitted off the surface of earth, which must be filtered through the water vapor in the atmosphere. After focusing the light onto hundreds of infrared detectors, the satellite sends the location of the missile launch back to earth - alerting of a potential missile attack.^[3]

Programs

United States

Artist's rendering of a SBIRS-GEO satellite.

Observation of a Delta II rocket launch by a SBIRS satellite in 2008.

The United States was the first country to attempt to establish a space-based early warning system. The goal was to detect Soviet ballistic missile launches and give 20 to 33 minutes notice of the missile's arrival (against 10 to 25 minutes for the BMEWS ground-based radar network).

The MIDAS satellites were launched between 1960 and 1966, and although they never entered a truly operational phase, they allowed the development of this type of satellite. DSP satellites in geostationary orbit took over in the early 1970s. Several generations of increasingly efficient DSP satellites followed one another until 2007.

Since 2011 the DSPs have been replaced by the SBIRS system, which includes dedicated satellites in geostationary orbit (SBIRS-GEO) and in low Earth orbit (SBIRS-LEO), as well as sensors on board Trumpet satellites for mixed use (wiretapping/warning) located in a Molniya orbit.

Soviet Union and Russia

The US-K and US-KS satellites developed under the Oko program were the first generation of Soviet early warning satellites. 86 US-K satellites were placed in a Molniya orbit between 1972 and 2010 and 7 US-KS satellites, of a very similar design, were placed in geostationary orbit between 1975 and 1997, the system becoming operational in 1980.

In 1983, a design error in the on-board software of the US-KS satellites led to the so-called fall equinox incident, which consisted of a false nuclear launch warning after a confusion between the heat caused by the reflection of solar radiation in clouds and that released by the launch of a nuclear missile.^[4]

Unlike their US counterparts, the US-K and US-KS only detect surface-to-surface ballistic missile launches, due to less sophisticated electronics. Later, the US-KS were replaced by the US-KMO, capable of detecting sea-to-land ballistic missile launches as well. The first of them would be placed in geostationary orbit in 1991.

In the early 1990s, after about ten years of operation, the coverage provided by these satellites was only partial, due to a reduction in the launch rate.

In 2014, the last 3 US-type satellites in service ceased their activities.^[5] They have been replaced starting in 2015 by a new generation of satellites: EKS, formerly known as Tundra.^[6][7][8]

Other countries

In France, the Direction générale de l'Armement carried out preliminary tests for the development of an early warning satellite. Infrared sensors were tested on two small experimental SPIRALE satellites launched in 2009. However, an operational satellite was not expected to be launched before the end of 2020.^[9]

China operates Huoyan-1 series satellites under the Tongxin Jishu Shiyan (TJS) program.^[10]

Satellite series

References:^[11] · ^[12] · ^[13] · ^[14] · ^[15] · ^[16] · ^[17] · ^[18] · ^[19] · ^[20] · ^[21] · ^[22] · ^[23] · ^[24] · ^[25] · ^[26]

Country	Series	Launch dates	Launches number / failures	Launcher	Mass	Orbit	Lifespan	Status	Comments
United States	MIDAS	1960-1966	12/4	Atlas- Agena	2 tons approx.	Low Earth orbit	from some weeks to 1 year	Retired	First generation; experimental; 4 versions
United States	DSP (phase I)	1970-1973	4/1	Titan-3C	907 kg	Geostationary orbit	1,25 years	Retired
United States	DSP (phase II)	1975-1977	3/0	Titan-3C	1043 kg	Geostationary orbit	2 years	Retired
United States	DSP (phase II MOS/PIM)	1979-1984	4/0	Titan-3C	1170 kg	Geostationary orbit	3 years	Retired
United States	DSP (phase II v2)	1954-1987	2/0	Titan-IVD Transtage	1674 kg	Geostationary orbit	3 years	Retired
United States	DSP (phase III)	1989-2007	10/1	Titan-IVD Transtage	2386 kg	Geostationary orbit	¿3 years?	¿Operational?	To be replaced by SBIRS
United States	SBIRS	2011-	12/0	Atlas V 401 or Delta IV-4M+(4,2)	4500 kg (SBIRS-GEO) 1000 kg (SBIRS-LOW)	Geostationary orbit / Low Earth orbit / Molniya orbit	12 years (SBIRS-GEO)	Operational	Geostationary satellites (SBIRS-GEO), satellites in low orbit (SBIRS-LEO), and sensors on Trumpet satellites in Molniya orbit
USSR/Russia	US-K	1972-2010	86/3	Molniya	2400 kg	Molniya orbit	1 year	Retired	Replaced by EKS
USSR/Russia	US-KS	1975-1997	7/0	Proton-K/Bloc-DM	2400 kg	Geostationary orbit	1 year	Retired	Almost identical to the US-K, replaced by the US-KMO
USSR/Russia	US-KMO	1991-2012	8/0	Proton-K/Bloc-DM-2	2600 kg	Geostationary orbit	5–7 years	Retired	Replaced by EKS
Russia	EKS	2015-	6/0	Soyuz-2.1b/Fregat-M	?	Molniya orbit	?	Operational

See also

• Missile defense
• Militarisation of space
• Space force
• Space domain awareness
• Space warfare

References

1. "Defense Support Program Satellites". United States Space Force. Retrieved 2024-07-29.
2. "Enhanced Space-Based Missile Tracking". Air & Space Forces Magazine. Retrieved 2024-07-29.
3. Hall, Cargill (July 1998). "MISSILE DEFENSE ALARM: THE GENESIS OF SPACE-BASED INFRARED EARLY WARNING" (PDF). NRO History – via nro.gov.
4. Dr. Geoffrey Forden (11 June 2001). "False Alarms in the Nuclear Age". PBS..
5. "Early warning". Russian strategic nuclear forces. 11 February 2015. Retrieved 25 August 2015.
6. Honkova, Jana (2013). "The Russian Federation's Approach to Military Space and Its Military Space Capabilities" (PDF). George C. Marshall Institute: 1–43. Honkova2013. Archived from the original (PDF) on 31 December 2014. Retrieved 16 June 2022.
7. Brian Harvey (2007). The Rebirth of the Russian Space Program - 50 Years After Sputnik, New Frontiers. Springer-Praxis. pp. 132–136. ISBN 978-0-387-71354-0. Harvey2007.
8. Zak, Anatoly (2 November 2022). "Soyuz launches a missile-detection satellite". RussianSpaceWeb. Retrieved 2 November 2022.
9. "PEA SPRIRALE" (in French). Optronique & Défense. 29 October 2010. Archived from the original on 31 December 2014. Retrieved 23 August 2022.
10. Clark, Phillip S. (January 2018). Becklake, John (ed.). "China's Shiyan Weixing Satellite Programme: 2004–2017" (PDF). Space Chronicle: A British Interplanetary Society Publication. 71 (1). London: 23. ISBN 978-0-9567382-2-6.
11. Gunter Dirk Krebs. "US-K (73D6)". Gunter's space page. Retrieved 31 December 2014.
12. Gunter Dirk Krebs. "US-KS (74Kh6)". Gunter's space page. Retrieved 31 December 2014.
13. Gunter Dirk Krebs. "US-KMO (71Kh6)". Gunter's space page. Retrieved 31 December 2014.
14. Gunter Dirk Krebs. "Tundra (14F142)". Gunter's space page. Retrieved 31 December 2014.
15. Gunter Dirk Krebs. "STSS 1, 2". Gunter's space page. Retrieved 31 December 2014.
16. Gunter Dirk Krebs. "SBIRS-GEO 1, 2, 3, 4, 5, 6". Gunter's space page. Retrieved 31 December 2014.
17. Gunter Dirk Krebs. "Trumpet-F/O-2' 1, 2". Gunter's space page. Retrieved 31 December 2014.
18. Gunter Dirk Krebs. "DSP 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 (Phase 3)". Gunter's space page. Retrieved 31 December 2014.
19. Gunter Dirk Krebs. "DSP 12, 13 (Phase 2 Upgrade)". Gunter's space page. Retrieved 31 December 2014.
20. Gunter Dirk Krebs. "DSP 8, 9, 10, 11 (Phase 2 MOS/PIM)". Gunter's space page. Retrieved 31 December 2014.
21. Gunter Dirk Krebs. "DSP 5, 6, 7 (Phase 2)". Gunter's space page. Retrieved 31 December 2014.
22. Gunter Dirk Krebs. "DSP 1, 2, 3, 4 (Phase 1)". Gunter's space page. Retrieved 31 December 2014.
23. Gunter Dirk Krebs. "MIDAS 1, 2 (MIDAS Series 1)". Gunter's space page. Retrieved 31 December 2014.
24. Gunter Dirk Krebs. "MIDAS 3, 4, 5 (MIDAS Series 2)". Gunter's space page. Retrieved 31 December 2014.
25. Gunter Dirk Krebs. "MIDAS 6, 7, 8, 9". Gunter's space page. Retrieved 31 December 2014.
26. Gunter Dirk Krebs. "RTS-1 1, 2, 3 (MIDAS-RTS-1 1, 2, 3 / AFP-461)". Gunter's space page. Retrieved 31 December 2014.

Bibliography

• Jacques Villain (2010). Satellites espions (in French). Paris: Vuibert. p. 232. ISBN 978-2-7117-2498-7.