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ASNARO-2 (Advanced Satellite with New system ARchitecture for Observation-2)

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ASNARO-2 is a Japanese SAR (Synthetic Aperture Radar) Earth imaging mission under development by the NEC Corporation and USEF (Institute for Unmanned Space Experiment Free Flyer). ASNARO-2 is a follow-up minisatellite mission of ASNARO. Like its predecessor, the project is funded by NEDO (New Energy and Industrial Technology Development Organization), a Department of METI (Ministry of Economy, Trade and Industry) of the Government of Japan. 1)


Figure 1: Illustration of the ASNARO-2 spacecraft (image credit: NEC)


ASNARO-2 is a minisatellite which features NEXTAR (Next Generation Star) bus. NEC’s small standard satellite bus module NEXTAR is based on NEC's long term experience in space division and is highly adaptive for various missions: remote sensing by optical or SAR (Synthetic Aperture Radar) sensor, ETS (Engineering Test & evaluation in Space) and scientific missions. The characteristics of small satellites are lighter, more affordable and have shorter delivery times. The NEXTAR program exhibits these characteristics. In addition, NEXTAR realizes high performance. 2) 3) 4) 5)

Figure 2 is the block diagram of ASNARO-2. The block diagram is almost identical to that of the ASNARO mission except for the mission control subsystem (purple box in Figure 2 on the upper right).


Figure 2: Block diagram of the ASNARO-2 bus (image credit: NEC)

Spacecraft mass

Bus: 305 kg (dry)
Payload: 220 kg
Propellant: 45 kg
Total mass: 570 kg

Design life

5 years

Electrical power

SAP Power: 1300 W (EOL)
For observation: 1200W

RF communications of payload data

X-band downlink, 16QAM(Quadrature Amplitude Modulation) scheme, data rate ~800 Mbit/s

Table 1: Some performance parameters of ASNARO-2


Figure 3: Alternate view of the deployed ASNARO-2 minisatellite (image credit: NEC)

Launch: The ASNARO-2 minisatellite was launched on 17 January 2018 (21:06:11 UTC, or 06:06:11 JST on 18.01.2018) on the Epsilon-3 vehicle from the JAXA Uchinoura Space Center, Kagoshima Prefecture, Japan. After 52 minutes and 35 seconds into the flight, the separation of ASNARO-2 was confirmed. 6) 7)

The Epsilon launcher is a three-staged solid propellant launch vehicle + compact liquid propulsion system.

Orbit: Sun-synchronous (dawn-dusk) near-circular orbit, altitude = 504 km, inclination = 97.4º. The same altitude as ASNARO-1 was selected to construct a constellation with ASNARO. The LTDN (Local Time of Descending Node) is 6:00 hours for securing sufficient battery charging time. The different local time from ASNARO makes it possible for multi-time observation by the constellation with ASNARO.

Mission status:

• March 8, 2019: According to Toshiaki Ogawa of NEC, the ASNARO-2 spacecraft and its payload are operating nominally in 2019. 8)

• September 25, 2018: JEOSS (Japan EO Satellite Service) is pleased to announce today to start the commercial sales of ASNARO-2 imagery products, the first Japanese commercial and very high resolution small X-band SAR (Synthetic Aperture Radar) satellite. The satellite is being used to acquire very high resolution imagery, 1.0 m resolution at Spotlight mode, and it is expected to be utilized as a supplement for larger satellites. 9)

- “In the forthcoming era of digital transformation, satellite remote sensing will be a part of “social big data” by fusing into IoT(Internet of Things). With high-end remote sensing ASNARO-2 data and state of the art ICT (Information and Communications Technology), JEOSS supports needs from human societies in the world to live in safety and security.” says Yasuo Horiuchi, CEO of JEOSS.

- JEOSS is planning to announce a worldwide reseller network very soon, and it is expected to expand ASNARO-2 imagery product sales in all over the world.

• March 16, 2018: NEC Corporation today announced the establishment of the "NEC Satellite Operation Center," a base of operations for satellites that is scheduled to be fully operational in April of this year. 10)

- The center will initiate operations for the ASNARO-2, a high-precision compact radar satellite that was developed with assistance from the Ministry of Economy, Trade, and Industry and launched in January of this year. The center uses NEC's GroundNEXTAR ground operations system and a high-security data center that was established using dedicated equipment. Moreover, the center can be used to operate multiple satellites simultaneously, as an expansion of operations is planned for the future.

- GroundNEXTAR is a high-quality ground system package developed by NEC based on the expertise the company has acquired through approximately 60 years working on the development and production of satellites and construction of ground systems. In addition to the primary operational functions provided by GroundNEXTAR, the system also offers visualization of satellite operations, especially 3D animation visualizations, and a distribution function for images. As a result, NEC plans to bring to market a wide range of images taken by ASNARO-2 in collaboration with Japan EO-Satellite Service, Ltd. (JEOSS) 11) starting in September of this year.

- "As the first satellite production company in Japan to provide comprehensive space solutions, including satellite production and utilization, NEC will contribute to solving a variety of social challenges through space projects such as satellite operation, data distribution and data utilization," said Hiroyuki Nagano, general manager, National Security Solutions Division, NEC Corporation.


Figure 4: Photo of the NEC Satellite Operation Center (image credit: NEC)

• March 13, 2018: NEC Corporation today announced the successful reception of images from its high-performance compact radar satellite, ASNARO-2, including images of a volcanic eruption in the Kirishima mountain range (Mount Shinmoe) in southwestern Japan. Images are scheduled to be available for public sale starting this September. 12)


Figure 5: Sample image of the area around the crater of Mount Shinmoe observed with ASNARO-2 on March 10, 2018 in spotlight mode (image credit: NEC)


Figure 6: The first images were taken from ASNARO-2 as it flew over Europe on February 4, 18 days after its launch, observed in strip-map mode. Although the image was taken at sunset, rural areas, vegetation and the condition of roads and rivers are clearly visible. Even the maturity of crops can be determined based on variations in their levels of brightness (image credit: NEC)

Sensor complement: XSAR

XSAR (X-band Synthetic Aperture Radar):

The XSAR instrument is designed and developed by the Mitsubishi Electric Corporation. The objective is to provide high-resolution imagery (< 1 m).


Spotlight mode

Stripmap mode

ScanSAR mode




< 1 m

< 2 m

< 16 m


> 10 km

> 12 km

> 50 km

Off-nadir angle



HH / VV (selectable)

Data Compression

1/2, 1/4, Non

Data quantization

8 bit

Table 2: Specification of the XSAR instrument


Figure 7: Illustration of the various observation modes (image credit: NEC)

Introduction of TWTA (Traveling Wave Tube Amplifier) technology:

Use of a MPA (Multi Port Amplifier), composed of TWTAs. This concept is adopted for the HPA (High Power Amplifier) of the small SAR instrument. At X-band, TWTA is suitable to the concentrated HPA. This is because the SSPA (Solid State Power Amplifier) implementation is not enough for this high power and high efficiency at X-band. For ASNARO-2, the gridded pulse TWTA is needed due to the lower power consumption. NEC has experience and heritage devices of CW (Continuous Waveform) TWTA for satellites and gridded pulse TWTA for aviation/ground implementations. The TWTA for ASNARO-2 was developed based on these heritages.


Figure 8: Photos of CW TWTAs for satellites developed by NEC (image credit: NEC)

1) ”Advanced Small Radar Satellite Called “ASNARO-2” to be Launched by the Third Epsilon Launch Vehicle,” METI, 12 Sept. 2017, URL:

2) Azusa Muta, Toshiaki Ogawa, Tatsuji Moriguchi, Akihiro Matsushita, Shoichiro Mihara, “Outline and Program status of ASNARO-2 (Advanced Satellite with New System Architecture for Observation) Satellite System,” Proceedings of the 9th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, April 8-12, 2013,

3) Yusuke Kobayashi, Toshiaki Ogawa, “Multiple Applications of NEXTAR Platform to Earth Observation Represented by ASNARO Satellite Series,” Proceedings of the 4S (Small Satellites Systems and Services) Symposium, Port Petro, Majorca Island, Spain, May 26-30, 2014

4) Y. Yokota, Y. Okada, K. Iribe, M. Tsuji, A, Ando, Y. Kunii, ”Newly developed X-band SAR system onboard Japanese small satellite “ASNARO-2”,” Published in: Synthetic Aperture Radar (APSAR), 2013 Asia-Pacific Conference, 23-27 Sept. 2013, Tsukuba, Japan, IEEE Xplore: 09 January 2014

5) ”NEC Small Radar Satellite "ASNARO-2",” NEC, URL:

6) ”Launch Result, Epsilon-3 with ASNARO-2 aboard,” JAXA Press Release, 18 January 2018, URL:

7) ”Launch Date of Epsilon-3 Encapsulating ASNARO-2,” JAXA Press Release, 8 Dec. 2017, URL:

8) Information provided by Toshiaki Ogawa, Satellite System Specialist, Space Systems Division of f NEC Corporation.

9) ”Japan EO Satellite Service, ltd (JEOSS) announces the Start of Commercial Operation,” JEOSS Press Release, 25 September 2019, URL:

10) ”NEC expands services from space - Establishes new "NEC Satellite Operation Center",” 16 March 2019, URL:


12) ”NEC releases images from the ASNARO-2 radar satellite,” NEC, 13 March 2018, URL:

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (

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