View source for BeppoSAX

{{Short description|Italian-Dutch satellite used for X-ray astronomy}}
{{Infobox spaceflight
| auto               = all
| name               = BeppoSAX
| names_list         = Satellite per Astronomia X

<!--image of the spacecraft/mission-->| image              = BeppoSAX.jpg
| image_caption      = Artist's conception of BeppoSax in space<br/>(credit: the Italian Space Agency (ASI) and BeppoSAX Science Data Center (SDC))
| image_size         = 240px

<!--Basic details-->| mission_type       = [[X-ray astronomy satellite|X-ray astronomy]]
| operator           = [[Italian Space Agency|ASI]]{{\}}[[Netherlands Agency for Aerospace Programmes|NIVR]]
| COSPAR_ID          = 1996-027A
| SATCAT             = 23857
| website            = {{URL|1=http://www.asdc.asi.it/bepposax/|2=www.asdc.asi.it/bepposax/}}
| mission_duration   = 7 years

<!--Spacecraft properties-->| manufacturer       = [[Alenia Aeronautica|Alenia]]<br />[[National Research Council (Italy)|CNR]]
| launch_mass        = {{convert|1400|kg|lb|order=flip|abbr=on}}
| payload_mass       = {{convert|480|kg|lb|order=flip|abbr=on}}
| dimensions         = {{convert|3.6|x|2.7|m|ft|abbr=on}}
| power              = 800&nbsp;W

<!--Launch details-->| launch_date        = {{start date|1996|04|30|04|31|7=Z}}
| launch_rocket      = [[Atlas-Centaur AC-78]]
| launch_site        = [[Spaceport Florida Launch Complex 36|LC-36B]], [[Cape Canaveral Air Force Station|Cape Canaveral]]

<!--end of mission-->| disposal_type      = decommissioned
| deactivated        = {{end date|2002|04|30|13|38|7=Z}}
| decay_date         = {{end date|2003|04|29|22|06|7=Z}}

<!--orbit parameters-->| orbit_epoch        = 30 April 1996, 03:31&nbsp;UTC<ref name="nasaNSSDC">{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1996-027A |title=NASA, NSSDC Master Catalog: 1996-027A |publisher=[[NASA]] |date=6 July 2015 |access-date=6 July 2015}}</ref>
| orbit_reference    = [[Geocentric orbit|Geocentric]]
| orbit_regime       = [[Low Earth orbit|Low Earth]]
| orbit_eccentricity = 0.00136
| orbit_periapsis    = {{convert|575|km|mi|abbr=on}}
| orbit_apoapsis     = {{convert|594|km|mi|abbr=on}}
| orbit_inclination  = 4&nbsp;degrees
| orbit_period       = 96.4&nbsp;minutes
| apsis              = gee

<!--Telescope parameters-->| telescope_type     = approximated [[Wolter telescope|Wolter type I]]<br />[[Coded aperture|Coded mask telescope]] (WFC)
| telescope_diameter = {{convert|6.8|to|16.2|cm|in|abbr=on}}
| telescope_focal_length = {{convert|1.85|m|ft|abbr=on}}
| telescope_area     = {{convert|22|to|600|cm2|sqin|abbr=on}}
| telescope_wavelength = [[X-ray]] to [[gamma ray]], 12&nbsp;[[nanometre|nm]]–4&nbsp;[[picometre|pm]] (0.1–300&nbsp;keV)
| instruments        = {{aligned table|fullwidth=y|style=text-align: left; font-size: 100%;
   |'''LECS'''| Low Energy Concentrator Spectrometer
   |'''MECS'''| Medium Energy Concentrator Spectrometer
   |'''HPGSPC'''&nbsp;| High Pressure Gas Scintillation Proportional Counter
   |'''PDS'''| Phoswich Detector System
   |'''WFC'''| Wide Field Camera
  }}
}}

'''BeppoSAX''' was an Italian–Dutch [[satellite]] for [[X-ray astronomy]] which played a crucial role in resolving the origin of [[gamma-ray burst]]s (GRBs), the most energetic events known in the universe. It was the first X-ray mission capable of simultaneously observing targets over more than 3 orders-of-magnitude of energy, from 0.1 to 300 [[kiloelectronvolt]]s (keV) with relatively large area, good (for the time) energy resolution and imaging capabilities (with a spatial resolution of 1 [[Minute of arc|arc minute]] between 0.1 and 10 keV). BeppoSAX was a major programme of the [[Italian Space Agency]] (ASI) with the participation of the [[Netherlands Agency for Aerospace Programmes]] (NIVR). The prime contractor for the space segment was [[Alenia Aeronautica|Alenia]] while [[Telespazio|Nuova Telespazio]] led the development of the [[ground segment]]. Most of the scientific instruments were developed by the [[National Research Council (Italy)|Italian National Research Council]] (CNR) while the Wide Field Cameras were developed by the [[Netherlands Institute for Space Research]] (SRON) and the LECS was developed by the astrophysics division of the [[European Space Agency]]'s [[European Space Research and Technology Centre|ESTEC]] facility.<ref name=saxov/>

BeppoSAX was named in honour of the Italian physicist [[Giuseppe Occhialini|Giuseppe "Beppo" Occhialini]]. SAX stands for "Satellite per Astronomia a raggi X" or "Satellite for X-ray Astronomy".<ref name=saxov>{{cite web|title=Mission overview|url=http://people.oas.inaf.it/amati/tesi/node8.html|access-date=October 13, 2022|publisher=Italian National Institute of Astrophysics}}</ref>

[[X-ray]] observations cannot be performed from ground-based telescopes, since Earth's atmosphere blocks most of the incoming radiation. One of BeppoSAX's main achievements was the identification of numerous [[gamma-ray burst]]s with extra-galactic objects.<ref>{{cite web|first=Marco |last=Feroci|title=Observation of Gamma-Ray Bursts by BeppoSAX|url=https://www.slac.stanford.edu/pubs/slacreports/reports08/ssi97-014.pdf|access-date=October 12, 2022|publisher=Stanford University}}</ref>

Launched by an [[Atlas-Centaur]] on 30 April 1996 into a low [[inclination]] (<4 degree) low-Earth orbit, the expected operating life of two years was extended to April 30, 2002, due to high scientific interest in the mission and the continued good technical status. After this date, the orbit started to decay rapidly and various subsystems were starting to fail making it no longer worthwhile to conduct scientific observations.<ref>{{cite web|first=Mark|last=Cleary|title=Atlas and Titan Space Operations at Cape Canaveral 1993-2006|url=https://afspacemuseum.org/wp-content/uploads/histories/AtlasTitan.pdf|work=USAF 45th Space Wing History Office|publisher=Air Force Space Museum|access-date=2022-10-14|archive-date=2022-12-01|archive-url=https://web.archive.org/web/20221201034842/https://afspacemuseum.org/wp-content/uploads/histories/AtlasTitan.pdf|url-status=dead}}</ref><ref name=saxstat/>

On April 29, 2003, the satellite ended its life falling into the Pacific Ocean.<ref>{{cite web|title=Latest news from the BeppoSAX project|url=https://www.ssdc.asi.it/bepposax/latestnews.html|access-date=October 12, 2022|publisher=Italian Space Agency}}</ref>

== Spacecraft characteristics ==
BeppoSAX was a three axes stabilized satellite, with a pointing accuracy of 1'. The main attitude constraint derived from the need to maintain the normal to the solar arrays within 30° from the Sun, with occasional excursions to 45° for some WFC observations. Due to the low orbit the satellite was in view of the ground station of [[Broglio Space Center|Malindi]] for only a limited fraction of the time. Data was stored on-board on a [[magnetic tape|tape unit]] with a capacity of 450&nbsp;Mbits and transmitted to ground every orbit during station passage. The average data rate available to instruments was about 60&nbsp;kbit/s, but peak rates of up to 100&nbsp;kbit/s can be retained for part of each orbit. With the solar panels closed, the spacecraft was 3.6 m in height and 2.7 m in diameter. The total mass amounts to 1400&nbsp;kg, with a payload of 480&nbsp;kg.<ref name=saxov/>

The structure of the satellite consisted of three basic functional subassemblies:
* the Service Module, in the lower part of the spacecraft, which housed all the subsystems and the electronic boxes of the scientific instruments.
* the Payload Module, which housed the scientific instruments and the [[star tracker]]s.
* the Thermal Shade Structure, that enclosed the Payload Module.<ref>{{cite journal|first=G.|last=Boella|title=BeppoSAX, the wide band mission for X-ray astronomy|url=https://aas.aanda.org/articles/aas/abs/1997/05/ds1221/ds1221.html|doi=10.1051/aas:1997136|pages=299–307|journal=Astronomy and Astrophysics Supplement Series|year=1997 |volume=122 |issue=2 |bibcode=1997A&AS..122..299B |doi-access=free}}</ref>

The primary sub-systems of the satellite are:
* The Attitude Orbital Control System (AOCS), that performed attitude determination and manoeuvred and operated the Reaction Control Subsystem in charge of orbit recovering. It included redundant [[magnetometer]]s, Sun acquisition sensors, three star trackers, six [[gyroscope]]s (three of which are for redundancy), three [[Magnetorquer|magnetic torquers]] and four [[reaction wheel]]s, all controlled by a dedicated computer. The AOCS ensured a pointing accuracy of 1' during source observations and manoeuvres with a slew rate of 10° per min.
* The On Board Data Handler (OBDH) was the core for data management and system control on the satellite and it also managed the communication interfaces between the satellite and the ground station. Its computer supervised all subsystem processor activities, such as those of each instrument, and the communication busses.<ref name=saxov/>

== Instrumentation ==
BeppoSAX contained five science instruments:
* Low Energy Concentrator Spectrometer (LECS)
* Medium Energy Concentrator Spectrometer (MECS)
* High Pressure Gas Scintillation Proportional Counter (HPGSPC)
* Phoswich Detector System (PDS)
* Wide Field Camera (WFC)

The first four instruments (often called Narrow Field Instruments or NFI) point to the same direction, and allow observations of an object in a broad energy band of 0.1 to 300 keV (16 to 48,000 [[Joule|attojoule]]s (aJ)).

The WFC contained two [[coded aperture]] cameras operating in the 2 to 30 keV (320 to 4,800 aJ) range and each covering a region of 40 x 40 degrees (20 by 20 degrees full width at half maximum) on the sky. The WFC was complemented by the shielding of PDS which had a (nearly) all-sky view in the 100 to 600 keV (16,000 to 96,000 aJ) band, ideal for detecting [[gamma-ray burst]]s (GRB).<ref>{{cite journal|first=R.|last=Jager|title=The Wide Field Cameras onboard the BeppoSAX X-ray Astronomy Satellite
|url=https://aas.aanda.org/articles/aas/full/1997/15/h0320/h0320.html|volume=125|pages=557–572|date=October 1997|journal=Astronomy and Astrophysics Supplement Series|issue=3 |doi=10.1051/aas:1997243 |bibcode=1997A&AS..125..557J |access-date=October 13, 2022|doi-access=free}}</ref>

The PDS shielding has poor angular resolution. In theory, after a GRB was seen in the PDS, the position was refined first with the WFC. However, due to the many spikes in the PDS, in practice a GRB was found using the WFC, often corroborated by a [[BATSE]]-signal. The position up to [[arcminute]] precision - depending on the signal to noise ratio of the burst - was found using the deconvoluted WFC-image. The coordinates were speedily sent out as an [[International Astronomical Union]] (IAU) and Gamma-ray burst Coordinate Network Circular. After this, immediate follow-up observations with the NFI and optical observatories around the world allowed accurate positioning of the GRB and detailed observations of the X-ray, optical and radio afterglow.

The MECS contained three identical [[X-ray astronomy detector|gas scintillation proportional counter]]s operating in the 1.3 to 10 keV (208 to 1602 aJ) range.<ref>{{cite web|title=The medium-energy concentrator spectrometer on board the BeppoSAX X-ray astronomy satellite|url=https://hera.gsfc.nasa.gov/docs/sax/instruments/new_mecs.html|access-date=October 12, 2022|publisher=nasa.gov|archive-date=October 13, 2022|archive-url=https://web.archive.org/web/20221013043818/https://hera.gsfc.nasa.gov/docs/sax/instruments/new_mecs.html|url-status=dead}}</ref> On 6 May 1997 one of the three identical MECS units was lost when a fault developed in the High Voltage power supply.<ref name=saxstat>{{cite web|title=BeppoSAX Status|url=https://hera.gsfc.nasa.gov/docs/sax/email/sax_status.html#17dec1996|access-date=October 13, 2022|publisher=nasa.gov|archive-date=October 14, 2022|archive-url=https://web.archive.org/web/20221014020724/https://hera.gsfc.nasa.gov/docs/sax/email/sax_status.html#17dec1996|url-status=dead}}</ref>

The LECS was similar to the MECS units, expect that it had a thinner window that allows photons with lower energies down to 0.1 keV (16 aJ) to pass through and operated in a "driftless" mode which is necessary to detect the lowest energy X-rays as these would be lost in the low field regime near the entrance window of a conventional GSPC. The LECS data above 4 keV (641 aJ) is not usable due to calibration issues probably caused by the driftless design. The LECS and MECS had imaging capability, whereas the high-energy narrow field instruments were non-imaging.<ref>{{cite news|title=The low-energy concentrator spectrometer on-board the SAX X-ray astronomy satellite|url=https://hera.gsfc.nasa.gov/docs/sax/instruments/parmar_etal_AaAS.html|access-date=October 13, 2022|publisher=nasa.gov|archive-date=October 14, 2022|archive-url=https://web.archive.org/web/20221014002621/https://hera.gsfc.nasa.gov/docs/sax/instruments/parmar_etal_AaAS.html|url-status=dead}}</ref>

The HPGSPC was also a gas scintillation proportional counter, operating at a high (5 atmospheres) pressure. High pressure equals high density, and dense photon-stopping material allowed detection of photons up to 120 keV (19,000 aJ).<ref>{{cite web|title=The High Pressure Gas Scintillation Proportional Counter on-board the BeppoSAX X-ray Astronomy Satellite|url=https://hera.gsfc.nasa.gov/docs/sax/instruments/hp.html|access-date=October 13, 2022|publisher=nasa.gov|archive-date=October 14, 2022|archive-url=https://web.archive.org/web/20221014002607/https://hera.gsfc.nasa.gov/docs/sax/instruments/hp.html|url-status=dead}}</ref>

The PDS was a crystal ([[sodium iodide]] / [[caesium iodide]]) scintillator detector capable of absorbing photons up to 300 keV (48,000 aJ). The spectral resolution of the PDS was rather modest when compared to the gas detectors, but the low background counting rate resulting from the low inclination BeppoSAX orbit and good background rejection capabilities meant that the PDS remains one of the most sensitive high-energy instruments flown.<ref>{{cite web|title=The high energy instrument PDS on-board the SAX X-ray astronomy satellite|url=https://hera.gsfc.nasa.gov/docs/sax/instruments/pds.html|access-date=October 13, 2022|publisher=nasa.gov|archive-date=October 14, 2022|archive-url=https://web.archive.org/web/20221014002603/https://hera.gsfc.nasa.gov/docs/sax/instruments/pds.html|url-status=dead}}</ref>

==Gallery==
{| align=center
| <gallery>
Image:BeppoSAX model.jpg|{{center|A model of BeppoSAX}}|alt=A model of BeppoSAX.
Image:BeppoSAX Particle Monitor.jpg|{{center|BeppoSAX particle monitor}}|alt=BeppoSAX particle monitor.
Image:BeppoSAX X-ray Concentrator Mirror Unit.jpg|{{center|BeppoSAX X-ray concentrator mirror unit}}|alt=BeppoSAX X-ray concentrator mirror unit.
Image:BeppoSAX Medium Energy GAS scintellation Proportional Counter.jpg|{{center|BeppoSAX Medium Energy GAS scintellation Proportional Counter}}|alt=BeppoSAX Medium Energy GAS scintellation Proportional Counter.
</gallery>
|}

== References ==
{{Reflist}}
{{commons category|BeppoSAX}}

==Other General References==
* BeppoSAX Mission Overview, ''Astronomy & Astrophysics Supplement Series'', Vol. 122, April II 1997, 299-307
* De Kort, N., ''Ruimteonderzoek, de horizon voorbij'', Veen/SRON, 2003
* Low Energy Concentrator Spectrometer (LECS) 0.1-10 keV, ''A&A Supplement series'', Vol. 122, April II 1997, 309-326
* Medium Energy Concentrator Spectrometer (MECS) 0.1-10 keV, ''A&A Supplement series'', Vol. 122, April II 1997, 327-340
* High pressure Gas Scintillator Proportional Counter (HPGSPC), ''A&A Supplement series'', Vol. 122, April II 1997, 341-356
* Phoswich Detection System (PDS) 15-300 keV, ''A&A Supplement series'', Vol. 122, April II 1997, 357-369
* Wide Field Camera 2-28 keV, ''A&A Supplement series'', Vol. 125, November 1997, 557-572 
* Piro, L. e.a., ''SAX Observer's Handbook'', 1995

== External links ==
{{Portal|Spaceflight}}
* [https://web.archive.org/web/20200201150943/http://www.asdc.asi.it/bepposax/ BeppoSAX Science Data Center]
* [http://heasarc.gsfc.nasa.gov/docs/sax/saxgof.html HEASARC BeppoSAX Guest Observer Facility]

{{Space observatories}}
{{Orbital launches in 1996}}

{{Use British English|date=January 2014}}

[[Category:Satellites formerly orbiting Earth]]
[[Category:Italian Space Agency]]
[[Category:Satellites of Italy]]
[[Category:Satellites of the Netherlands]]
[[Category:Space telescopes]]
[[Category:Spacecraft launched in 1996]]
[[Category:Spacecraft which reentered in 2003]]
[[Category:X-ray telescopes]]