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JERS-1

The Japan Earth Resources Satellite (JERS-1 aka Fuyo 1) was launched in February, 1992, into a 570-km, sun-synchronous orbit. The 12-year effort to field the moderate resolution SAR and multi-spectral payload was a joint venture by NASDA, which was responsible for the spacecraft, by the Ministry of International Trade and Industry, which developed the payload instruments, and by the Science and Technology Agency. Mitsubishi Electric was the prime contractor aided by Toshiba, Nippon Electric, and the Japanese Resources Observation Systems Organization.

The 1,340 kg JERS-1 consists of a net rectangular bus (0.9 m by 1.8 m by 3.2 m) with a single 2-kW solar array (3.5 m by 7.0 m) and an eight-segmented SAR antenna (2.4 m by 11.9 m when deployed). The spacecraft is 3-axis stabilized with a payload of nearly 500 kg and a design life of two years. Frequent orbital adjustments are required to maintain the 44-day repeating groundtrack.

The spacecraft carries two closely matched Earth observation sensors: the SAR and the OPS multi-spectral imager. The SAR operates at a frequency of 1.275 GHz with a peak power of 1.3 kW, a 75-km swath, and an 18-m resolution. The SAR mission was placed in jeopardy for two months when the large radar antenna failed to deploy fully. On 4 April 1992 the space craft signaled that the first stage of deployment was finally accomplished, and by 9 April the full antenna array was in position. Images returned by the SAR in late April lived up to expectations, although some minor interference problems appeared later in the year (References 586-592).

The OPS system is comprised of a 3-band, CCD Visible and Near-lit Radiometer (VNIR) using 0.52-0.60 µm, 0.63-0.69 µm, and 0.760.86 µm regimes and a 4-band, CCD Short Wavelength IR Radiometer (SWIR) sensitive to 1.60-1.71 µm, 2.01-2.12 µm, 2.13-2.25 µm, and 2.27-2.40 µm. The resolution of the OPS is matched to that of the SAR at 13 m. A mission data recorder is available to store images until downlinked by the mission data transmitter at 8.15 GHz and 8.35 GHz. JERS-1 continued to experience sensor difficulties, and in late 1993 the SWIR failed due to a cooling problem. The remainder of the spacecraft's instruments were still operational at the end of 1994 (References 593-595).

On October 11, 1998 a malfunction occurred on JERS-1. The Okinawa Station could not receive the signal from the satellite at 11:50am on October 12, 1998, and so a terminate command was sent from the Santiago Station in Chile at about 12:30pm on the same day, thus terminating the operation of the satellite.

The mission of JERS-1 was to last only two years, but in the end it was possible to obtain observation data on the earth (with regard to resources, disasters, the environment etc.) from the satellite for approximately six-and-a-half years. Some representative examples of the research results achieved through use of these data are the retrieval of potential oil mine in Turpan basin of China, the clarifying of the reality of deforestation in the Amazon tropical rainforest and of the situation of diastrophism (deformation of the earth's crust) caused by the activity of the volcano Mt. Iwateyama.