NinjaSat: 6U-size CubeSat observatory for monitoring bright X-ray compact objects
Abstract
We present a 6U-size CubeSat X-ray observatory, NinjaSat, scheduled to be launched into a Low-Earth Orbit in February 2023. X-ray astronomy has been promoted by large satellites equipped with highly sensitive instruments. However, the observation time of large satellites is shared among many users and is therefore limited for each X-ray object. In contrast, NinjaSat will conduct a flexible X-ray observation program, such as long-term observations simultaneously with telescopes at other wavelengths, for bright X-ray sources that are either impossible or often difficult to observe with modern large X-ray satellites due to instrument limitations. The NinjaSat attitude control system using a star tracker, five sun sensors, and four reaction wheels enables a pointing observation with an accuracy of less than 0.1°. NinjaSat is equipped with two sets of 1U-size non-imaging Gas Multiplier Counters (GMCs), main science payloads, and Radiation Belt Monitors (RBMs) for the safe operation of GMCs. GMC consists of a gas cell equipped with a gas electron multiplier, an X-ray collimator of a 2.1° field of view, a high voltage supply and analog signal processing board, a digital signal processing board, and an iron-55 calibration source. NinjaSat is sensitive to 2--50~keV X-rays with a total effective area of 32~cm^2 at 6~keV by filling the gas cell with a xenon/argon/dimethyl ether (75%/24%/1%) gas mixture with a pressure of 1.2~atm at 0°C. RBM uses a Si-PIN photodiode (9 × 9~mm^2, 500~μm thick) to detect unexpected radiation increases such as solar flares and prevent GMC from being damaged by electric discharge. The GMC and RBM proto-flight models have passed space environment tests (radiation tolerance tests, vibration tests, and thermal vacuum tests). We are currently in the final stages of flight models fabrication and calibration.
- Publication:
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44th COSPAR Scientific Assembly. Held 16-24 July
- Pub Date:
- July 2022
- Bibcode:
- 2022cosp...44.1990T