Spektr-RG (SXG)

Spektr-RG [Lavochkin]

The Spektr-RG (SXG) was a Russian-international observatory-class mission with participation from the US, UK, Italy, Germany, France, Denmark, Hungary, Switzerland, Finland, Türkiye (Turkey), and Israel. It was to carry a complement of more than ten scientific instruments and detectors that span the electromagnetic spectrum from the extreme ultraviolet to gamma rays (0.06-100 MeV), with angular resolution from 10 arc-seconds to a few arc-degrees. It was cancelled in 2002, but revived later in 2005 as a different mission under the same name, Spektr-RG (SXG).

The payload was to consist of:

• three grazing-incidence X-ray telescopes (SODART A and B, JET-X),
• a UV telescope (EUVITA),
• an X-ray telescope with coded-aperture instruments (MART),
• a Bragg spectrometer, two gaseous position-sensitive proportional counters (LEPC/HEPC),
• two solid-state Si(Li) detectors (SIXA),
• a gaseous scintillation proportional counter, X-ray CCD arrays,
• a stellar X-ray polarimeter (SXRP),
• an X-ray all-sky monitor (MOXE),
• and spectrometers for measuring gamma-ray bursts (DIOGENE and SPIN).
• Tel Aviv University Ultra Violet Explorer (TAUVEX)

The scientific objectives include high-resolution spectroscopy, timing observations, imaging of weak X-ray sources, determining X-ray source positions, monitoring transient events, investigating the origin of the diffuse X-ray background, and understanding the nature of gamma-ray bursts.

SXG will be in a highly elliptical, high-earth orbit. It will operate three out of four days. On the fourth day, there will be a reduction in observing time when the spacecraft traverses the Earth's magnetosphere. The SXG spacecraft consists of a main body and a pointing platform. The main body is triaxially stabilized to an accuracy of 2.5 arc-seconds. The spacecraft can be pointed to any direction in the sky, constrained only by the instruments' thermal control demands, detector solar illumination restrictions and telemetry requirements. The spacecraft pointing can be changed up to ten times per day via stored commands. Data stored on-board will be transmitted to the ground station once per day via a 2 Mbps telemetry link. A mission lifetime of at least three years is planned.

Originally the satellite was to be built on the Spektr bus, a derivative of the US-KMO-Bus and to be launched on a Proton-K Blok-DM-2 booster.

Initial launch date was set to 1995, but later postponed as far as 2008, until it was finally cancelled in 2002 due to lack of funding. However, some of the instruments have been completed, e.g., an X-ray telescope by Leicester University (JET-X) and an ultraviolet telescope by Tel-Aviv University (TAUVEX). TAUVEX was the remanifested in modified form on the Indian GSat 4, but was finally grounded.

Although partially built, financial issues prevented the X-ray and Gamma-ray observatory to be launched.

The project was later revived in 2005 also under the name Spektr-RG (SXG), but with a different instrument suit.