MOS Marine Observation Satellite
Space-based oceanography is conducted in Japan by two Marine Observation Satellites (MOS) placed in sun-synchronous orbits of approximately 910 km with an inclination of 99.1 degrees. After 10 years of development MOS 1 (aka Momo 1 or "Peach tree") was launched in February, 1987, and was followed by MOS 1b (Momo 1b) in February, 1990, into an orbital plane only a few degrees away from MOS 1.
The Marine Observation Satellite (MOS-1) was Japan's first earth observation satellite. The three-axis stabilized spacecraft carried (1) a Multispectral Electronic Self-scanning Radiometer (MESSR) that collected data from both land and sea, (2) a Visible and Thermal Infrared Radiometer (VTIR) to measure sea surface temperature, (3) a Microwave Scanning Radiometer (MSR) to provide information on sea ice, snowfall, water vapor content at the ocean and in the atmosphere, and (4) a Data Collection System (DCS) transponder to collect observation data from drifting buoys. The spacecraft had a box-type shape with deployable solar panels. It was composed of two cubes, a bus module and a mission module, on which the three sensors were mounted. The spacecraft followed a sun-synchronous orbit with equatorial crossings in the descending node maintained between 10:00 a.m. and 11:00 a.m. local time. The mission life was designed to be 2 years.
The Japanese Marine Observation Satellite-1B (MOS-1B) was the second Earth resources satellite in the MOS series to be launched by NASDA to monitor atmospheric water vapor, ocean currents, sea surface temperature, ice floe dynamics, chlorophyll concentration in the oceans, and vegetation and agricultural land applications. The MOS-1B carried the same three sensors as the MOS-1A: a Multi-spectrum Electronic Self-Scanning Radiometer (MESSR), a Visible and Thermal Infrared Radiometer (VTIR), and a Microwave Scanning Radiometer (MSR). Data was transmitted real-time to the Hatoyama Earth Observation Center for processing and is available through the Data Service Department, Remote Sensing Technology Center of Japan (RESTEC). The satellite also included a Data Collection System (DCS) Transponder designed to be a forerunner of the Japanese TDRSS, used to collect and relay information from surface Data Collection Platforms (DCPs) and locate DCPs based on the Doppler frequency of received signals. The satellite is a 1.26 x 1.48 x 2.4 meter high box-shape of aluminium honeycomb construction with a single solar array of three 1.51 meter wide panels. The satellite is controlled in three axes by momentum wheels and four IN hydrazine thrusters.
The program objectives include:
- "a Development of observation sensors; verification of their functions and performances, and experimental observation of the Earth (in particular the oceans) using such sensors;
- Basic experiments on a data collection system (DCS);
- Establishment of fundamental technologies for Earth observation satellites" (Reference 583).
Funded and managed by NASDA, the MOS program selected NEC Corporation as the prime contractor with significant assistance by Mitsubishi Electric, Toshiba, and Fujitsu. Each 740-kg, 3-axis-stabilized spacecraft consists of a box-shape bus (1.3 m by 1.5 m by 2.4 m) with a single solar array (2.0 m by 4.5 m). The selected orbit permits a repeating groundtrack with a period of 17 days.
The MOS payload consists of four primary classes of instruments. Two 70-kg Multi-spectral Electronic Self-Scanning Radio-meters (MESSR) return images in four bands (0.51-0.59 µm, 0.61-0.69 µm, 0.72-0.80 µm, and 0.80-1.1 µm) with a ground resolution of 50 m and a swath of 100 km. The fields-of-view of the two MESSR sensors are slightly overlapped (15 km) to provide stereo viewing. The 25-kg Visible and Thermal Infrared Radiometer (VTIR) operates in one visible and three IR bands: 0.5-0.7,µm, 6-7 µm, 10.5-11.5 µm, and 11.5-12.5 µm with ground resolutions of 900 m (visible) and 2,700 m (JR) and a swath of 1,500 km. The 54 kg Microwave Scanning Radiometer (MSR) is tuned to two frequencies: 23.8 GHz and 31.4 GHz. The swath is 317 km with respective resolutions of 23 km and 32 km. Finally, the Data Collection System Transponder (DCST) collects data from DCP's transmitting in the 400 MHz band and relays the information to data acquisition and processing facilities at a frequency of 1.7 GHz. MESSR and VTIR data are transmitted at 1.7 GHz and 8 GHz, while MSR data are downlinked at 2 GHz.
As of 1993 MOS 1 and MOS 1b were expected to remain operational until about 1997 and 2001-2002, respectively (References 583-585). Momo-1 sensors finished their operations on November 29,1995. Momo-1b(MOS-1b), which has the same functions as Momo-1, finished its opration on April 17, 1996. Other MOS satellites were planned throughout the 1990's, but the program ended with the first pair.
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