Editing X-ray astronomy (section)

==Explorational X-ray astronomy==
[[File:Ulysses 2 orbit.jpg|thumb|right|Ulysses' second orbit: it arrived at [[Jupiter]] on February 8, 1992, for a [[swing-by maneuver]] that increased its inclination to the [[ecliptic]] by 80.2 degrees.]]
Usually observational astronomy is considered to occur on Earth's surface (or beneath it in [[neutrino astronomy]]). The idea of limiting observation to Earth includes orbiting the Earth. As soon as the observer leaves the cozy confines of Earth, the observer becomes a deep space explorer.<ref name=Kawakatsu>{{Cite journal|author=Kawakatsu Y |title=Concept study on Deep Space Orbit Transfer Vehicle |journal=Acta Astronautica |date=Dec 2007 |volume=61 |issue=11–12 |pages=1019–28 |doi=10.1016/j.actaastro.2006.12.019 |bibcode = 2007AcAau..61.1019K }}</ref> Except for [[Explorer 1]] and [[Explorer 3]] and the earlier satellites in the series,<ref name=Smith>{{cite web|author=Smith W |title=Explorer Series of Spacecraft |url=https://history.nasa.gov/explorer.html}}</ref> usually if a probe is going to be a deep space explorer it leaves the Earth or an orbit around the Earth.

For a satellite or space probe to qualify as a deep space X-ray astronomer/explorer or "astronobot"/explorer, all it needs to carry aboard is an XRT or X-ray detector and leave Earth's orbit.

''[[Ulysses (spacecraft)|Ulysses]]'' was launched October 6, 1990, and reached Jupiter for its "[[Gravity assist|gravitational slingshot]]" in February 1992. It passed the south solar pole in June 1994 and crossed the ecliptic equator in February 1995. The solar X-ray and cosmic gamma-ray burst experiment (GRB) had 3 main objectives: study and monitor solar flares, detect and localize cosmic [[gamma-ray burst]]s, and in-situ detection of Jovian aurorae. ''Ulysses'' was the first satellite carrying a gamma burst detector which went outside the orbit of Mars. The hard X-ray detectors operated in the range 15–150 keV. The detectors consisted of 23-mm thick × 51-mm diameter CsI(Tl) crystals mounted via plastic light tubes to photomultipliers. The hard detector changed its operating mode depending on (1) measured count rate, (2) ground command, or (3) change in spacecraft telemetry mode. The trigger level was generally set for 8-sigma above background and the sensitivity is 10<sup>−6</sup> erg/cm<sup>2</sup> (1 nJ/m<sup>2</sup>). When a burst trigger is recorded, the instrument switches to record high resolution data, recording it to a 32-kbit memory for a slow telemetry read out. Burst data consist of either 16 s of 8-ms resolution count rates or 64 s of 32-ms count rates from the sum of the 2 detectors. There were also 16 channel energy spectra from the sum of the 2 detectors (taken either in 1, 2, 4, 16, or 32 second integrations). During 'wait' mode, the data were taken either in 0.25 or 0.5 s integrations and 4 energy channels (with shortest integration time being 8 s). Again, the outputs of the 2 detectors were summed.

The ''Ulysses'' soft X-ray detectors consisted of 2.5-mm thick × 0.5&nbsp;cm<sup>2</sup> area Si surface barrier detectors. A 100&nbsp;mg/cm<sup>2</sup> beryllium foil front window rejected the low energy X-rays and defined a conical FOV of 75° (half-angle). These detectors were passively cooled and operate in the temperature range −35 to −55&nbsp;°C. This detector had 6 energy channels, covering the range 5–20 keV.
[[File:PIA21061-Pluto-DwarfPlanet-XRays-20160914.jpg|thumb|center|300px|{{center|X-Rays from Pluto}}]]