ADEOS (Advanced Earth Observing Satellite) / Midori
ADEOS (Midori) is the first Japanese (NASDA) satellite mission with international cooperation. In Japan, the ADEOS satellite is also referred to as `Midori', meaning `green'. The overall objective of the mission is dedicated to Earth environmental research: integrated observation of geophysical parameters, global observation of land, ocean and atmospheric processes (ocean color and sea surface temperature). In addition, communication demonstrations are planned for the study (feasibility) of interorbit links, called IOCS (Inter-Orbital Communication Subsystem). 1) 2)
Note: The Japanese space agency NASDA (National Space Development Agency) changed its name on Oct. 1, 2003 to JAXA (Japan Aerospace Exploration Agency), Tokyo, Japan. JAXA is the new name (merger) of the three former Japanese space organizations into a single national agency, namely: NASDA (National Space Development Agency of Japan), ISAS (Institute of Space and Astronautical Science), and NAL (National Aerospace Laboratory of Japan).
Figure 1: Line drawing of the ADEOS spacecraft (image credit: JAXA) 3)
The spacecraft is comprised of a bus with a deployable solar array (one wing). Satellite mass = 3560 kg at lift-off, payload mass = 1300 kg, power = 4.5 kW, S/C size: 4 m x 4 m x 5 m. The spacecraft is made up of thermally, electrically and mechanically independent units, which facilitate its integration and testing, including the C&DH (Communications and Data Handling Subsystem), the EPS (Electrical Power Subsystem), and the AOCS (Attitude and Orbital Control Subsystem). 4) 5) 6) 7) 8)
The AOCS employs a three-axis strap-down attitude detection system and a zero-momentum attitude control system, attitude error <0.3º, attitude stability <0.003º/s. Mission design life=3 years.
The satellite features an automatic, autonomous operation function capable of operating a large number of mission instruments, and inter orbital communication equipment to transmit observation data via data relay satellite. The IOCS (Inter-Orbital Communication Subsystem) transmits observation data via ETS-VI (Engineering Test Satellite-VI) and COMETS (Communications and Broadcast Engineering Test Satellite).
The ADEOS spacecraft was developed by the Mitsubishi Electric Corporation, Tokyo. NEC Corporation and Toshiba Corporation were subcontractors to Mitsubishi Electric Corporation.
Table 1: Some spacecraft parameters of ADEOS
Launch: The launch of ADEOS took place on August 17, 1996 with the H-II launch vehicle from TNSC (Tanegashima Space Center), Japan.
Orbit: Sun-synchronous sub-recurrent polar orbit; apogee = 804.6 km; perigee = 789.0 km; orbital period = 100.8 min, 10:30 AM local sun orbit (on descending node). Ground repeat cycle=41 days (subcycle = 3 days), inclination = 98.625º.
RF communications: ADEOS provides onboard recording (MDR=Mission Data Recorder (three instruments) and LMDR = Low Speed Mission Data Recorder). Observation data rates: AVNIR (M): 60 Mbit/s, AVNIR (P): 60 Mbit/s, OCTS: 3.0 Mbit/s. Polder: 0.882 Mbit/s. IMG: 0.9 Mbit/s. ILAS: 0.517 Mbit/s. NSCAT: 2.9 kbit/s. TOMS: 0.7 kbit/s.
RF comuunications: TT&C: Uplink frequency (S-band) = 2.0 GHz (CMD and ranging), downlink frequency = 2.2 GHz (TLM and ranging), command bit rate = 500 bit/s.
IOCS frequencies: S-band (low rate mission data), Ka-band (120 Mbit/s max).
Figure 2: Artist's rendition of the ADEOS spacecraft (image credit: JAXA)
• The ADEOS spacecraft operations were terminated: ADEOS operated nominally for some period (10 months), but then suffered several malfunctions and stopped functioning on June 30, 1997 after an apparent loss of power due to structural damage in its solar array. This loss of an observatory like ADEOS was definitely a great blow, particularly for all involved in the mission and of course the data user community. 9)
Immediately after this great loss of the spacecraft, Jaxa established a Task Team to investigate the cause. The investigation lasted about three months and focused on the solar paddle subsystem (PDL) and the attitude orb