Hitomi (space telescope)

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Hitomi
Hitomi
Type: X-ray satellite
Country: JapanJapan Japan
Operator: JAXA
COSPAR-ID : 2016-012A
Mission dates
Dimensions: 2.7 t
Size: 14 m
Begin: February 17, 2016, 08:45 UTC
Starting place: Tanegashima YLP-1
Launcher: H-II A-202 F-30
Status: in orbit; broken on March 26, 2016
Orbit data
Rotation time : 96 min
Track height: 550 km
Orbit inclination : 31 °
Apogee height :  originally 576.5 km
Perigee height :  originally 574.4 km

Hitomi (formerly ASTRO-H , initially non-thermal Energy eXploration Telescope NeXT) was the name of a Japanese X-ray satellite of JAXA . As usual in Japan, the satellite was renamed after its successful launch - Hitomi ( ひ と み ) means eye, pupil in Japanese. The mission took place u. a. in cooperation with NASA , ESA and the CSA .

The satellite should continue the investigations started by ASTRO-D and record X-rays and gamma rays in the range between 0.3 and 600  keV with various instruments.

Hitomi was supposed to map cosmic objects in the gamma radiation range from 0.3 keV to 80 keV and record them spectroscopically up to 600 keV . For technical reasons, X-ray telescopes have a long focal length . Hitomi had a boom six meters in length and a total length of approximately 12 meters.

Due to technical problems, the satellite broke in orbit during the commissioning phase.

prehistory

The planning of the mission and the associated basic research began in 2007. In October 2009, a cooperation agreement between Japan and the Netherlands for the development and construction of the satellite was signed. It should start in 2013. However, this appointment could not be kept later. The basic design of the satellite was completed in May 2010. The various individual device tests were carried out from April 2012 to March 2013. In May 2014 the devices were integrated into the housing and the tests for the entire satellite began. The gamma detectors were only finally tested in spring 2015 and installed in April 2015. In the second half of 2015, among other things, the vacuum test and a vibration test of the 6-meter satellite (with a compressed optical bench) took place. It was finally presented to the press and public in December 2015 and the start date was set for February 12, 2016. Due to the weather conditions, the start was postponed on that day and finally took place on February 17, 2016.

Mission objectives

The satellite's investigations should primarily focus on galaxies and black holes .

  • Investigation of the history of formation and the influence of supermassive black holes on their galaxies and galaxy clusters by observing mass ejections from black holes and from X-ray binary stars with a black hole (e.g. Cygnus X-1 )
  • Investigation of the formation, the inner interaction (between the galaxies) and the long-term development of galaxy clusters as well as their kinetic energy and the contained dark matter through the X-ray Doppler effect that the interplay of forces of plasma creates in these clusters
  • Investigation of the history of the formation of heavy elements (such as carbon and oxygen ) in the universe by observing supernova remnants (since heavy elements were only created by stars and their explosion and did not exist before)
  • Investigation of the physical principles of neutron stars and white dwarfs by observing the X-ray and soft gamma radiation which are caused by the extreme density and the strong magnetic fields and the like. a. due to the superfluidity of protons
  • Investigation of the distortion of spacetime and the assumed rotation at and from black holes also by observing X-ray binary stars with a black hole (such as Cygnus X-1)
  • Investigation of the acceleration of cosmic rays by observing their origin (e.g. in supernovae, black holes or galaxy clusters)

Mission history

On February 17, 2016, the satellite was launched with an H-II launcher . The orbit reached by the satellite had an apogee of 576.5 km (planned 575.0 km) and a perigee of 574.4 km (planned 574.0 km). The deviations were marginal so that the satellite was considered to have been successfully placed. The deployment of the solar panels proceeded as expected, all systems were working normally.

The so-called critical operational phase begins after the satellite is suspended and ends when the stable operation of all systems has been established. The execution of the measures, u. a. the commissioning of the cooling system (−273.1 ° C), the test of the soft X-ray spectrometer (X-ray spectrometer for soft X-ray radiation below 10 keV) and the extension of the optical bench were successfully completed on February 29th.

This was followed by the performance review phase, in which the functionality of all scientific instruments was checked. For this purpose, known celestial bodies were observed with the space telescope. The phase should be completed after six weeks and the calibration phase should start in mid-April.

However, that did not happen. A test carried out five hours before the incident showed abnormal levels of altitude, power supply and temperature inside the satellite. These deviations from the planned values ​​were also measured in the tests three hours and around one hour before the incident. Since the last test at 01:52 a.m. (CET) on March 26, 2016, no telemetry data has been received from the satellite. However, isolated radio signals could be received from a satellite, which were sent from Hitomi's expected position.

The incident happened at 02:42 a.m. (CET) on March 26, 2016 (± 11 min).

JAXA suspects the events in the following order: After the alignment maneuver on the Markarian galaxy , the attitude control system triggered an incorrect attitude determination. It signaled that the satellite would rotate. The reaction wheel was then activated to stop the supposed rotation. This actually caused the satellite to rotate. A magnetic torque generator, which was supposed to weaken the momentum of the reaction wheel, also contributed to the rotation of the satellite due to the incorrect position determination. The critical situation was finally identified by the attitude control system. It put the systems in a safety mode. However, the alignment thrusters were activated based on the incorrect values. This thrust further increased the rotation. The parts that experienced the greatest rotational forces, such as B. the solar panels and the optical bench now broke off from the satellite.

Additional damage to the satellite, e.g. B. by an explosion is not excluded. According to Jonathan McDowell also a gas leak or explosion could have occurred the battery.

The results of the radar observations showed a change in the orbit time. JSpOC confirmed on March 27, 2016 that there are at least five separate parts in the vicinity of the satellite. On April 1, JSpOC identified eleven separate parts that can be assigned to the satellite (including the main body). JAXA was able to identify two separate parts with the resources at their disposal.

Hitomi was still in the test phase, which should be completed with the observation tests at the end of 2016. In April 2016, JAXA ruled out the resumption of operations for the satellite. Based on the flight path calculation by JSpOC, a re-entry of parts into the earth's atmosphere was expected as early as the end of April. The first parts entered the earth's atmosphere on April 20 and 24, 2016. JAXA assumes that the parts of the satellite will burn up upon re-entry.

Instruments

The satellite had four telescopes, two gamma-ray detectors and four different detectors for X-rays. All instruments could be used in parallel.

The Hard X-ray Telescope (HXT) has two identical mirror telescopes for hard X-rays. The mirrors are cone-shaped and the multi-layer reflective surface enables an energy range of 5 to 80 keV to be displayed. The different layers in the deeply layered mirror have different periodic lengths. Some are also coated with carbon or platinum . The HXT mirrors each have a diameter of 45 cm. By placing the HXI image sensors at the end of the optical bench (6 m) of the satellite, a focal length of 12 meters and an effective area of ​​300 cm² is possible. In addition to external reflection, it also works with a system of Bragg reflection . The HXT is a cooperation project with the CSA.

The duplicate Hard X-ray Imager (HXI) consist of four layers of 0.5 mm thick semiconductor detectors made of silicon (as used in the inner ATLAS detector in the LHC of CERN ) and a layer with a 0.5–1 mm thick CdTe detector. The soft (more) X-ray radiation (5-30 keV) is absorbed by the silicon detectors, while the hard X-ray radiation (20-80 keV) penetrates through it and is recorded in the CdTe detector. The HXI camera systems are attached to the end of the optical bench.

The satellite has two telescopes for soft X-rays (SXT-S and SXT-I). The SXT-S works in conjunction with the SXS spectrometer, while the SXT-I works together with the SXI camera system (based on CCD storage technology). Both telescopes are identical and have a diameter of 45 cm. The connected systems are at the other end of the satellite (but not on the optical bench), so both have a focal length of 5.6 meters.

The Soft X-ray Spectrometer (SXS) is cooled down to −273.15 degrees Celsius. Penetrating X-ray- charged photons increase the temperature minimally, this allows the X-ray energy to be determined. The SXS forms the core of the satellite and is technically very advanced compared to previous X-ray telescopes. It has a measuring range of 6 keV. Due to various advantages, the spectrometer measures iron compounds in particular . The SXS uses NASA's microcalorimetry technology (a further developed method of calorimetry ), which only requires a few micrograms of a sample to be examined.

The Soft X-ray Imager (SXI) is a wide-angle camera system which is cooled down to -120 degrees Celsius. By combining four large X-ray CCDs, it achieves a viewing angle of 38 ° and thus complements the SXS, which has a smaller angle due to its high spectral resolution. The SXI works in conjunction with the SXT-I. It depicts an energy range below 10 keV. In addition to the image function, it is also a spectrometer for soft X-rays.

The two soft gamma ray detectors (SGD) are mounted on the side of the satellite and do not interact with any of the four telescopes. They have no focus or angle of view and therefore cannot produce any images. You will work with semiconductor detectors based on the Compton effect . There are silicon and CdTe detectors (see HXI) which measure in an energy range between 10 and 600 keV. Due to the different modes of operation of the silicon and CdTe detectors, the amounts of energy and the exit direction can be determined for all events above 50 keV with the help of the Compton effect.

Successor Mission

The parties involved plan to launch a largely identical replacement satellite, the X-ray Astronomy Recovery Mission (XARM) , in 2020 .

Web links

swell

  1. ↑ a b University of Cambridge | Institute of Astronomy: Successful launch of Hitomi February 17, 2016, accessed March 28, 2016.
  2. ↑ Planned path data according to ASTRO-H Overview. ISAS, accessed on January 6, 2016 .
  3. ↑ ASTRO-H successfully launched and named “Hitomi”. nasaspaceflight, February 17, 2016, accessed February 17, 2016 .
  4. ↑ Concerns grow for X-ray astronomy satellite ASTRO-H. nasaspaceflight, March 28, 2016, accessed April 10, 2016 .
  5. ↑ a b High Energy Astrophysics: The New X-ray Telescope ( English ) ISAS. 2008. Retrieved June 17, 2009.
  6. ↑ Topics List ASTRO-H. JAXA, July 31, 2016, accessed May 29, 2016 .
  7. ↑ a b Hitomi Experience Report May 24, 2016. (PDF) JAXA, accessed on May 29, 2016 (English).
  8. ↑ Mysteries to be investigated by "Hitomi" (ASTRO-H). JAXA, February 17, 2016, accessed on May 29, 2016 .
  9. ↑ X-ray Astronomy Satellite “Hitomi” (ASTRO-H) Orbit Calculation Result. JAXA, February 18, 2016, accessed July 31, 2016 .
  10. ↑ X-ray Astronomy Satellite (ASTRO-H) Solar Array Paddles Deployment and Name Decided. JAXA, February 17, 2016, accessed April 10, 2016 .
  11. ↑ X-ray Astronomy Satellite "Hitomi" (ASTRO-H) Completion of Critical Operation Phase. JAXA, February 29, 2016, accessed April 10, 2016 .
  12. ↑ a b c d Status of X-ray Astronomy Satellite Hitomi (ASTRO-H) 04/06/2016. (PDF) JAXA, accessed on April 10, 2016 (English).
  13. ↑ JSpOC Update Astro-H. Joint Space Operations Center, March 28, 2016, accessed April 10, 2016 . Incident, 02:42 a.m. (CET) on March 26, 2016 (± 11 min): Time confirmed by the Joint Space Operations Center (JSpOC) and JAXA.
  14. ↑ a b Status of X-ray Astronomy Satellite Hitomi (ASTRO-H) April 15, 2016. (PDF) JAXA, accessed on April 10, 2016 (English).
  15. ↑ Japan Loses Contact With New Space Telescope. In: Phenomena. Retrieved March 28, 2016 .
  16. ↑ ABC News: Japan: Trouble Reaching Innovative New Space Satellite. In: ABC News. Archived from the original on April 10, 2016 ; accessed on July 31, 2016 .
  17. ↑ JSpOC break-up Astro-H. Joint Space Operations Center, April 1, 2016, accessed April 10, 2016 .
  18. ^ Canadian Space Agency - Upcoming Japanese X-ray Space Observatory
  19. ↑ a b Hard X-ray Imaging System. JAXA, February 17, 2016, accessed on May 29, 2016 .
  20. ↑ a b c d e f Instrument Positions on Spacecraft. JAXA, February 17, 2016, accessed on May 29, 2016 .
  21. ↑ a b Soft X-ray Spectroscopy System. JAXA, February 17, 2016, accessed on May 29, 2016 .
  22. ↑ NASA: NASA Selects Explorer Mission of Opportunity Investigations . NASA. June 20, 2008. Retrieved June 17, 2009.
  23. ↑ Microcalorimetry. Spektrum, December 31, 1998, accessed on May 29, 2016 (German).
  24. ↑ Soft X-ray Imaging System. JAXA, February 17, 2016, accessed on May 29, 2016 .
  25. ↑ Soft Gamma-ray Detector. JAXA, February 17, 2016, accessed on May 29, 2016 .
  26. ↑ 「ひ と み」 後 継 機 を 容 認 ＝ 概算 要求 盛 り 込 む - 馳 文科 相. Retrieved December 19, 2016 (Japanese).
  27. ^ NASA and JAXA to develop replacement X-ray astronomy telescope. Accessed April 2, 2017 .