it control system (AOCS).
• JAXA completed the on-orbit initial checkout of all equipment aboard ADEOS as planned. The satellite began the routine operational phase on November 26, 1996, and the project began providing OCTS and AVNIR standard products for the ADEOS PIs on January 1, 1997. 10)
• The critical phase of ADEOS ended after the 22nd revolution on August 19, 1996. JAXA started verifying the functions of the bus system and the mission instruments on that date. The initial mission checkout of ADEOS will continue for 90 days (until the middle of November 1996). 11)
Sensor complement: (OCTS, AVNIR, NSCAT, TOMS, POLDER, IMG, ILAS, RIS)
OCTS (Ocean Color Temperature Scanner):
OCTS is a mechanical scanning (whiskbroom) radiometer, and a JAXA (NASDA) core sensor. Objectives: Ocean color and sea surface temperature measurements (ocean primary productivity, interaction between the ocean and the atmosphere and environmental studies). OCTS offers 12 measurement bands from 0.402 - 12.5 µm. Swath width = 1400 km; ±20º along-track tilting. Spatial resolution: approx. 700 m. Operation requirements: global observation of the Earth during daytime (TIR channel during night if required). 12)
Table 2: Definition of OCTS parameters
The OCTS sensor consists of a scanning radiometer with an optical system, a detector module and an electrical unit. OCTS employs a catoptric optical system and a mechanical rotating scanning method with a mirror (due to wide spectral coverage). OCTS can be tilted about the along-track axis to prevent sea surface sun glitter. The IR detectors are cooled to 100 K by a large radiant cooler facing deep space. Calibration: solar and internal lamp for VNIR, deep space and black body for IR. 13) 14) 15) 16)
Figure 3: The observation concept of the OCTS instrument
Figure 4: Internal configuration of the SRU (SCanning Radiometer Unit) of OCTS (image credit: NASDA)
Figure 5: First ocean color image of the Sea of Japan and the East China Sea taken by OCTS on October 1, 1996 (image credit: JAXA) 17)
AVNIR (Advanced Visible and Near-Infrared Radiometer):
AVNIR is a NASDA core sensor, an optoelectronic scanning radiometer using CCD detectors. Objective: Land and coastal zone observations, measurement of reflected sunlight from the Earth's surface. AVNIR is comprised of two units, SRU (Scanning Radiometer Unit) containing all the optical components (a catadioptric Schmidt telescope system is used, the spectrum is dispersed by a prism and interference filter), and ELU (Electronic Unit). 18) 19) 20)
Spectral range: 5 bands from 0.42 - 0.89 µm (multispectral bands: 0.42-0.50, 0.52-0.60, 0.61-0.69 and 0.76-0.89 µm, panchromatic band (visible): 1 band 0.52-0.69 µm). Spatial resolution: multispectral bands: ~16 m (IFOV=20 µrad), panchromatic band: about 8 m (IFOV =10 µrad). Swath width = 80 km (FOV=5.7º). Observation requirements: regional observation according to user requests; simultaneous multispectral and panchromatic operation. 21) 22)
The AVNIR instrument has the capability to tilt the observation field by ±40º about the across-track axis. The 0.42-0.50 µm band is useful for coastal zones and lakes. The scanning radiometer unit uses a catadioptric Schmidt optical system (telescope) to reduce aberration in a wide field of view. Calibration of sensor using solar light and internal lamps. The radiometric absolute accuracy is ±10%, the onboard calibration accuracy =±5%. The large linear array CCDs offer 5,000 and 10,000 detector elements for high spatial resolution. Instrument mass=250 kg, power=300W.
Figure 6: The observation geometries of the AVNIR instrument
Figure 7: Illustration of the AVNIR instrument (image credit: NASDA)
Figure 8: Block diagram of the AVNIR instrument (image credit: NASDA)
Figure 9: AVNIR image of the island reefs in the Great Barrier Reef of northeast Australia (image credit: JAXA)
NSCAT (NASA Scatterometer):
NSCAT is a NASA/JPL sensor. Objective: Measurement of surface wind speeds and directions over the global oceans, coverage every two days under all weather and cloud conditions. NSCAT is a micro