Symposium on Remote Sensing for Resources Development and Environmental Management/Enschede /August 1986
© 1987 Balkema, Rotterdam. ISBN 90 6191 674 7
Comparison of MOMS and Thematic Mapper, data for geoscientific
application and aspects for future development of multispectral
sensors
J.Bodechtel
AGF -Working Group Geoscientific Remote Sensing, Faculty of Geosciences, University of Munich, FR Germany
The missions of the German Modular Optoelectronic Multispectral Scanner MOMS aboard two flights of the
United States Space Transportation System STS demonstrated the feasibility of a novel concept with regard
to both technical and scientific objectives. On account of the successful missions a cooperation was
agreed between the German Federal Minister of Research and Technology and NASA for comparting MOMS observations
with the more familiar operational Landsat-Thematic Mapper data over selected testsites as a means of
obtaining some relative measure of performance. This paper summarizes the results obtained and presents the
M0MS-02, a further experimental representative in the MOMS program aiming at the realzation of an operational
system for the midnineties.
INTRODUCTION
The past successes in the field of remote sensing -
based on the Landsat-MSS family - have supported
the definition of a new generation of earth
observation satellites. With the launch of the
Thematic Mapper sensoraboard the Landsat-4 and -5
spacecrafts the U.S.A. are able to offer multi
spectral imagery with a ground pixel size of 30 m
and 7 spectral bands from which an optimum
combination can be selected.
In February 1986, France launched its SPOT into
orbit. It is designed as an operational system and
incorporates the new CCD technology. Particularly
worth to be mentioned is its high ground resolution
of 20 m in the multisprectral and 10 m in the
panchromatic operating mode. SPOT is also the
first scanner providing an experimental track-by
track stereo imaging mode with tiltable mirrors.
Within that scope the MOMS instrument development
has been constituted by the Federal Minister for
Research and Technology 8MFT. Due to its flexible
modular concept, MOMS can be modified and adapted
to fulfil specific requirements for a large
variety of geoscientific tasks.
M0MS-01 TECHNICAL CONCEPT
The two experimental missions of M0MS-01 on the
carrier structure SPAS aboard Shuttle flights
STS-7/June '83 and STS-11 (%1-8)/February '84 were
the first spacetests of an optoelectronic Scanning
system for earth resources applications. The
missions were to verify the technical concept under
space conditions and to prove the applicability of
high resolution CCD-data for geoscientific
thematic mapping up to sales 1 : 50 000 /
1 : 25 000.
A primary concept underlying the MOMS design and
program is that of sensor and mission versatility.
The modular construction facilitates the use of
different sensor units or peripheral devices to
suit the application and carrier platform for each
mission.
The modularity like
- optical system per channel, exchange of lenses or
filters,
- focal plane assembly (detector arrays and immedi
ate electronics variable in type and number),
- different orientation of modules for stereo
imaging enables e.g. the combination of high
spatial resolution modules with medium spatial/
high spectral resolution modules (different focal
lengths and ground pixel sizes), and an easy
refurbishment or the use of newest developed
technology (e.g. sensor arrays)(Fig. 1).
Detector elements are charge coupled devices (CCD's)
with 1723 pixels per array (Reticon CCPD 1728).
Scan line extension beyond 1 CCD array (up to 6 per
focal plane feasible) is done by the dual optics
principle (Fig. 2).
The essential advantages of the "pusch-broom"
technology are:
- simple, compact construction, no moving mechanical
parts,
- central geometry in the scanline/acquisition of a
total scan line simultaneously,
- digitized image coordinate data for the pixel
coordinate correlation and their radiometric
intensity,
- high geometric and radiometric precision, reduced
geometric data preorocessing effort.
MOMS/THEMATIC MAPPER COMPARISON
During the 2 M0MS-01 missions aboard Space Shuttle
Challenger, a total number of 26 image sequences,
could be recorded under mostly optimum weather
conditions due to controlling the data acquisition
in real-time on the basis of a global weather
information network (Fiq. 4).
Out of these data takes 5 testsites v/ere selected
for a mutual exchange of MOMS and Thematic Mapper
data. The testsites for the joint evaluation
include a section of the Red Sea Hills in Northern
Sudan, the Cordillera coast and mountain chains of
the Atacama desert near Antofagasta, Chile, a scene
in the vicinity of Nairobi, Kenya, a desertifica
tion threatened section of the Sahel channel in
Mali and in Saudi Arabia the cities of Jeddah,
Makkah and At'Taif (see circles in Fig. 4).
For comparison with the 575 - 625 nm MOMS band the
Landsat-TM bands 2 and 3 (520 - 600 nm and 630 -
690 nm) were used. The MOMS 825 - 975 nm band was
compared with the TM 790 - 900 nm band (see Fig. 5).
Table 1 provides a breakdown of the differences
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