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JAXA's MAXI (Monitor of All-sky X-ray Image) is an International Space Station (ISS) based all-sky X-ray scanner, which consists of X-ray slit cameras with high sensitivity. It continuously monitors astronomical X-ray objects over a broad energy band (0.5 to 30 keV).

MAXI monitors the X-ray variability once every 96 minutes for more than 1,000 X-ray sources covering the entire sky on time scales from a day to a few months.

As an all-sky monitor, MAXI employs slit cameras. They determine one direction of X-ray sources within the narrow field of view of the slit that is orthogonally oriented to a one-dimensional position-sensitive X-ray detector. As an X-ray source moves according to the motion of the International Space Station, another position of the X-ray source is determined when the sources are captured by the collimated field of view of the camera.

The International Space Station orbits around the Earth every 96 minutes. During this time, Maxi’s two semicircular (arc-shaped) fields of view will scan the whole sky once.

MAXI employs two types of position-sensitive detectors, gas proportional counters and X-ray CCDs, aligned to two fields of views to observe both the zenith and horizontal directions.

  • Gas Slit Camera (GSC) - A slit camera with a gas proportional counter covers the 2 to 30 keV energy band with its large detection area. One-dimensional position-sensitive gas proportional counter with 10 µm carbon anode wires, based on the method of charge division.·MAXI is equipped with 12 counters with a total effective area of 5000 cm2.
  • Solid-state Slit Camera (SSC) - A slit camera with peltier-cooled X-ray sensitive CCD chips covers the 0.5 to 10 keV energy band with high resolution. The CCD chips are made in Japan. The pixel size is 24 × 24 µm, and there is a total of 1024 × 1024 pixels. MAXI is equipped with two cameras. One camera has 16 CCD chips, for a total effective area of 200 cm2.
Nation: Japan
Type / Application: Astronomy, X-ray
Operator: JAXA
Contractors: JAXA
Equipment: GSC, SSC
Configuration: Attached ISS payload
Propulsion: None
Power: Via ISS
Lifetime: 1 year (planned); 6 months reached
Mass: 500 kg
Orbit: 400 km × 400 km, 51.6° (typical)
Satellite COSPAR Date LS Launch Vehicle Remarks
MAXI N/A 15.07.2009 CCK LC-39A Shuttle with Endeavour F23 (STS-127), JEF (JEM-EF), JLE (JEM-ELM-ES), SEDA-AP, ICS, ANDE-2 AA, ANDE-2 PA, Bevo 1, AggieSat2