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CubeSat X-ray
Observatory

NinjaSat

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About NinjaSat

NinjaSat is a 6U-size X-ray CubeSat observatory operated by RIKEN equipped with Xe-filled proportional counters covering the energy range of 2–50 keV. The satellite focuses on agile observations of bright X-ray compact sources. NinjaSat was launched into a Sun-synchronous orbit on November 11, 2023. After completing the satellite and payload commissioning phase, science operations officially began on February 23, 2024. During its 604 days of payload operation, NinjaSat successfully observed 32 X-ray sources. Its final communication was received by a Lithuanian UHF ground station at 21:31:30 UTC on September 17, 2025, after which the satellite re-entered Earth’s atmosphere and concluded its mission.

 

Scientific Objectives

  • Contribution to observations of transient celestial objects, leveraging high mobility.
  • New discoveries through multi-wavelength coordinated observations with ground-based observatories and other space telescopes, as well as long-term dedicated monitoring.
  • Providing observational data of neutron stars to contribute to the discovery of continuous gravitational waves.

Fact Sheet

  Value or Note
Units 6U (NanoAvionics M6P)
Weight 8.14 kg
Power 16.4 W daily average
Downlink 60 MB/day in normal operation
Orbit Sun Synchronous Orbit
Altitude about 510 km (as of Jul. 2024)
Launch 2023 Nov. 11 10:49 (PST) (SpaceX Transporter-9)
 End of operation At 21:31:30 UTC on 2025 Septembar17, the spacecraft made its final contact with a Lithuanian UHF station, then re-entered the atmosphere, ending its operations.
Payloads 2×GMC and 2×RBM
GMC Gas Multiplier Counter
10×10×10 cm3 (1U size), 1.2 kg
Energy range: 2-50 keV
Time resolution: 61 μs
Effective area: 16 cm2 (6 keV)
RBM Radiation Belt Monitor
Monitors the flux of charged particles in the orbit.
0.07U size, 70 g
NinjaSat
GMC
RBM
CubeSat X-ray Observatory NinjaSat (Top photo)
GMC (Middle photo)
RBM (Bottom photo)

Achievements

Observation Results

NinjaSat Papers and Proceedings

Original papers (All original papers are open access.)
Proceedings of SPIE 2025
Proceedings of Small Satellite Conference 2025
Proceedings of Small Satellite Conference 2024
Proceedings of Small Satellite Conference 2023
Proceedings of MPGD 2022
Proceedings of SPIE 2020
The Astronomer's Telegram (ATel)

Project history

2020/8

Gas Chamber Testing.

2020

Collimator Measurement.

2020, @KEK

Gas chamber X-ray irradiation test.

2020

RBM thermostatic chamber test.

2020

Gas fill complete!

2021/3, @名古屋大学

FEC/DAQ Thermal Vacuum Test.

2021

GMC Parts Assembly.

2022/03~11, @SAITEC

GMC vibration test.

2022-01~06, @JAXA

GMC Thermal Vacuum Test.

2022-07, @HIMAC

GMC Radiation Resistance Test.

2022-11, @KEK

GMC X-ray measurement test.

~2023-07

Assembling the entire satellite

Credit: Kongsberg NanoAvionics

2023-11-11 18:49 UTC

SpaceX launched a Falcon 9 rocket carrying NinjaSat as part of its Transporter-9 mission.

2023-11-11 19:43:13 UTC

NinjaSat was deployed from the Falcon 9 rocket.

2023-11-14 ~ 2024-01-21

Satellite commissioning phase.

2024-01-22

Payload activation started.

2024-02-10

Observing the Crab Nebula for calibration.

The Crab pulsar's rotation period of 33.8 milliseconds was measured, confirming the GMC detector's clock is highly precise.

2024-02-23

Scientific observations start.

2024-02-27 ~ 2024-03-17

Observation of the new source SRGA J144459.2-604207.

(ATel #16495: https://astronomerstelegram.org/?read=16495)

2024-05

Observation was suspended due to high solar activity.

2024-06

Observation of EXO 0748–676; successfully detected X-ray bursts.

We successfully observed an X-ray burst from EXO 0748-676, a neutron star and low-mass star binary, which has become more active after six years. https://astronomerstelegram.org/?read=16678)

2024-07-13 ~ 2024-09-29

 Long-term monitoring (~3 months) of T CrB.

We conducted long-term monitoring observations of T CrB (T Coronae Borealis), a recurrent nova likely to erupt.

2024-11

Successfully conducted follow-up observations of MAXI J1752-457 in MAXI-NinjaSat collaboration.

We successfully conducted follow-up observations of the new celestial object MAXI J1752-457, discovered by the all-sky X-ray monitor MAXI aboard the International Space Station. The time from MAXI's discovery report to the NinjaSat observation was just 2.5 hours. http://astronomerstelegram.org/?read=16903)

2025-01

Successful follow-up observation of the new X-ray transient MAXI J1744-294.

We made follow-up observations of the X-ray flare in the galactic center region reported by the all-sky X-ray monitor MAXI. We reported the results to the Astronomer’s Telegram (ATel). https://astronomerstelegram.org/?read=17009)

2025/7

Discovery of a resurgence of periodic X-ray bursts from neutron star GS 1826-238.

This was the first time it had been around for about 10 years, and this time the outbursts were occurring at intervals of about 1.6 hours, the shortest interval in recorded history. (Iwata et al: https://astronomerstelegram.org/?read=17245 )

2025/09/17 21:31:30 UTC

Re-entry into the atmosphere.

At 21:31:30 UTC on 2025 Septembar17, the spacecraft made its final contact with a Lithuanian UHF station, then re-entered the atmosphere, ending its operations.

Since launch, the satellite has observed 32 X-ray celestial bodies during 604 days of payload operation, accomplishing all of its planned missions.

Students are taking the lead and thriving

Students affiliated with RIKEN have been involved in the development of NinjaSat from the very beginning and continue to play a key role in its operations.

Public Relations

Real-time updates are available on [X (formerly Twitter) account @ninjasat_xray].

Team member

Toru Tamagawa¹, Teruaki Enoto²˒¹, Takao Kitaguchi¹, Wataru Iwakiri³, Yo Kato¹, Masaki Numazawa⁴, Tatehiro Mihara¹, Tomoshi Takeda⁵, Naoyuki Ota¹˒⁶,
Sota Watanabe¹˒⁶, Arata Jujo¹˒⁶, Amira Aoyama¹˒⁶, Satoko Iwata¹˒⁶, Takuya Takahashi¹˒⁶, Kaede Yamasaki¹˒⁶, Takayuki Kita³, Soma Tsuchiya¹˒⁶, Yosuke Nakano¹˒⁶, Mayu Ichibakase¹², Chin-Ping Hu⁷, Hiromitsu Takahashi⁵, Yuto Yoshida¹˒⁶, Hiroki Sato¹˒⁸, Shoki Hayashi¹˒⁶, Yuanhui Zhou¹˒⁶, Keisuke Uchiyama¹˒⁶, Tsubasa Tamba⁹, Hirokazu Odaka¹⁰, Kentaro Taniguchi¹˒¹¹
¹RIKEN, ²Kyoto University, ³Chiba University, ⁴Tokyo Metropolitan University, ⁵Hiroshima University, ⁶Tokyo University of Science, ⁷National Changhua University of Education, ⁸Shibaura Institute of Technology, ⁹ISAS/JAXA, ¹⁰Osaka University, ¹¹Waseda University, ¹²Rikkyo University

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