The UHURU satellite (Uhuru) is the first orbital X-ray observatory. For the first time, a satellite mission was entirely devoted to the study of celestial X-ray sources . Previous experiments on the X-ray emission of celestial sources were carried out exclusively on suborbital rockets, which significantly limited the useful time of their instruments.
| Uhuru | |
|---|---|
 Uhuru Satellite Map | |
| Organization | NASA |
| Wave range | X-rays |
| NSSDC ID | 1970-107A |
| Location | Geocentric orbit |
| Orbit type | Low apogee |
| Orbit height | ~ 560/520 km |
| Circulation period | 96 minutes |
| Launch date | December 12, 1970 |
| Launch place | San Marco Platform |
| Orbiter | Scout |
| Duration | 3 years |
| Departure Date | March 18, 1973 |
| Weight | 141.5 kg |
| Scientific instruments | |
| proportional gas meters |
| Site | heasarc.gsfc.nasa.gov/do... |
The Uhuru Observatory (also known as SAS-A , Small Astronomical Satellite-A , or Explorer 42) was the first in a series of small astronomical satellites of the US space agency NASA (the next satellites in this series are SAS-2 and SAS-3 ) . The main objective of the observatory was to conduct an overview of the entire sky in the X-ray energy range.
The main mode of operation of the observatory was scanning the sky due to rotation around its axis with a period of ~ 12 minutes. In special cases, it was possible to significantly slow down the satellite’s rotation - up to one revolution in ~ 1.4 hours. It was this regime that was used by researchers when observing x-ray pulsars discovered by the Uhuru observatory.
The satellite was launched into orbit by the Scout B launch vehicle from the marine spaceport - the San Marco platform off the coast of Kenya in 1971. Marjorie Townsend, the head of the Small Astronomical Satellites (SAS) program, proposed to name the satellite “Uhuru”, which means “freedom” in Swahili , in honor of the 7th anniversary of Kenya’s independence, when the SAS-A observatory was launched.
Tools
The instruments of the observatory were two proportional gas meters with an effective area of 840 square meters. see each. The effective working range of the instruments is 2–20 keV . The lower limit of the operating range was determined by transmitting a beryllium window and transmitting thermal protection of the instruments. The background count rate of the detector was suppressed by separating the signals by pulse-shape discrimination and anti-matching protection. Events recorded by devices were recorded in 8 energy channels. Two pairs of detectors were placed under collimators of different sizes - 0.52 ° × 5.2 ° and 5.2 ° × 5.2 °.
Results
The results of the observatory were a series of fundamental discoveries in astronomy. Namely:
- Discovery of X-ray pulsars - accreting rotating neutron stars [1]
- The discovery that accreting neutron stars - X-ray pulsars - are in binary systems [1]
- X-ray discovery of galaxy clusters [2]
- The discovery of non-stationary radiation of x-ray sources. From the fact that the X-ray radiation of the Lebed X-1 source showed significant variability on a time scale of ~ 70 ms , it was first made possible to make the assumption that the central massive object in this system is a black hole [3] [4] . This fact is the first experimental confirmation of the real existence of black holes.
- First obtained a map of the entire sky in the x-ray range. The catalog, compiled according to the results of the observatory, included 339 sources [5] Notes
- ↑ 1 2 Discovery of Periodic X-Ray Pulsations in Centaurus X-3 from UHURU
- ↑ A Strong X-Ray Source in the Coma Cluster Observed by UHURU
- ↑ X-Ray Pulsations from Cygnus X-1 Observed from UHURU
- ↑ X-ray astronomy in the UHURU epoch and beyond / Newton Lacy Pierce Prize Lecture
- ↑ The fourth Uhuru catalog of X-ray sources
Other SAS satellites
- SAS-2
- SAS-3
See also
- List of spacecraft with x-ray and gamma detectors on board