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production of digital elevation models, (2) a six-channel
shortwave infrared radiometer (SWIR), and (3) a five-
channel thermal infrared radiometer (TIR). All three radi-
ometers can be operated independently and all three are
individually pointable. The instrument features high
spatial and radiometric resolution. The nadir-viewing
swath width is 60 km. With its pointing capability,
ASTER is capable of viewing any point on Earth every
16 days. Because of its polar orbit, it can view any point
above 45° every 7-9 days and any point above 69° every 3-
4 days. It takes 48 days to provide full surface coverage.
The ASTER characteristics are given in Table 1.
Table 1. ASTER
Data rate
62 Mbps
Radiometer Spectral range
VNIR Nadir bands
0.52-0.60 u
0.63-0.69 u
0.76-0.86 u
Stereoscopic band
0.76-0.86 u
SWIR 6 bands
1.6-1.7 ju
2.145-2.185 ju
2.185-2.225 u
2.235-2.285 u
2.295-2.365 u
2.360-2.430 u
23 Mbps
TIR 5 bands
8.125-8.475 u
8475-8.825 u
8.925-9275 u
10.25-10.95 ju
10.95-11.65 u
4.1 Mbps
Spatial resolution
«0.596 15m
Radiometric resolution
<0.5%-1.3% 30m
<3K 90m
Instrument and spacecraft resources are allocated to support
an 8% average duty cycle. ASTER data will be acquired
and processed according to specific user requirements
identifying acquisition time, gain, wavelength region, and
data product. For daytime observations, the user may
request that any or all of the three subsystems be operated.
For nighttime observations, typically only the TIR sub-
system will be employed, but it is possible to request
both TIR and SWIR at night for hot volcanic targets.
Current plans are that all EOS investigators, and other
scientists approved by NASA or MITI will be allowed to
submit requests for data acquisition over their targets.
Additionally, the ASTER Science Team, working with
the IDS Teams, will define targets such as active vol-
canoes, which should be monitored routinely, and a one-
ume global land surface map will be created over the six-
year life of the mission. Data, once acquired, will be
available to all investigators.
SUMMARY
The next decade should prove to be an exciting one for
geologists using thermal infrared remote sensing. Just as
Landsat developed a large user community in the 1970s
when multispectral VNIR data became available over
users' areas of interest, we anticipate that the advent of the
sensors discussed here will develop a demand for high-
spatial-resolution multispectral, thermal infrared data. It
is important that the technology be developed to allow
continued improvement in these types of instruments.
ACKNOWLEDGMENTS
This work was supported in part by NASA contract to the
Jet Propulsion Laboratory, California Institute of Techno-
logy.
REFERENCES
Asrar, G., and D.J. Dokken, editors, 1993. EOS
Reference Handbook, NP-202.
Durpaire, P., et al., 1995. IRSUTE: A multispectral IR
observation instrument on a small satellite. In: SPIE,
San Diego.
Hook, S.J., and A.B. Kahle, 1995. The Micro-Fourier
Transform Interferometer (WFTIR) — A new field spec-
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996
