BeppoSAX

BeppoSAX was an Italian-Dutch satellite for X-ray astronomy. The satellite structure and control was built by various Italian and Dutch companies, while the scientific instruments were developed by the Italian CNR[?] science research institute.

BeppoSAX was named in honour of the Italian astronomer Giuseppe "Beppo" Occhialini[?]. SAX stands for "Satellite per Astronomia i raggi X" or "Satellite for X-ray astronomy".

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 bursts with extra-galactic objects (see the linked article for details).

Launched in in 1996, the expected operating life of two years was extended to April 30, 2002. After this date, the orbit was decaying too rapidly and various subsystems were failing. Final deorbit was planned for 2003.

In April 30, 2003, the satellite ended its life falling into the Pacific Ocean.

Spacecraft characteristics:

• Weight: 1,400 Kg
• Dimensions: 3.6 meters high, 2.7 meter diameter
• Solar cell power: 3 KW
• Orbit height: 600 KM
• Data generated: 1 Gigabyte each orbit (90 minutes)

Intrumentation

BeppoSAX contained five science instruments:

• LECS or Low Energy Concentrator Spectrometer
• MECS or Medium Energy Concentrator Spectrometer
• HPGSPC or High Pressure Gas Scintillation Proportional Counter
• PDS or Phoswich Detector System
• WFC or Wide Field Camera

The four first intruments (often called Narrow Field Instruments or NFI) point to the same direction, and allow observations of an object in a broad energy band of 0.1-300 keV.

The WFC contained two coded aperture[?] cameras operating in the 2-30 keV range and each covering a region of 20 by 20 degrees on the sky. The WFC was complemented by the shielding of PDS which had a (nearly) all-sky view in the 100-600 keV band, ideal for detecting gamma ray bursts (GRB).

PDS shielding has poor angular resolution, but after a GRB was seen in the PDS, the position was refined first with the WFC. After this, follow-up observations with the NFI allowed accurate positioning of the GRB and detailed observations of the X-ray afterglow.

The MECS contained three indentical gas scintillation proportional counters[?] operating in the 1.3-10 keV range. LECS was almost identical to the MECS units, expect that it had a thinner window that allows photons with lower energies (down to 0.1 keV) to pass through. High background contamination makes the LECS data above 4 keV unusable. LECS and MECS had imaging capability, whereas the high-energy narrow field instruments were non-imaging.

HPGSPC was also a gas scintillation proportional counter, but high (three atmospheres) pressure. High pressure equals high density, and dense photon-stopping material allowed detection of photons up to 120 keV.

PDS was a crystal scintillator[?] (Natrium Iodide / Cesium Iodide) capable of stopping photons up to 300 keV. The spectral resolution of PDS was rather modest when compared to the gas detectors.