Full text: Remote sensing for resources development and environmental management (Volume 3)

- estimate the radiometric resolution and dynamic 
range by calculating statistics and entropy; 
- evaluate the spatial resolution and dynamic range 
by calculating statistics and entropy; 
- evaluate the spatial resolving powers by 
o performing an edge analysis, 
o estimating point spread functions, 
- compare the spectral capabilities, 
- analyse the MOMS within scan noise, MOMS and TM 
between scan noise and signal-to-noise ratios. 
Tables 2, 3, 4 and 5 show different results ob 
tained in the testsites. 
Fig. 6 shows an enlarged section of the testsite in 
Kenya, processed by NASA/GSFC. The MOMS-01 in 
frared band is compared to TM band 4. During the 
STS-7 mission the MOMS infrared band turned out to 
be out of focus. Due to the modular concept the 
focal length of the dual lens optics could be 
adjusted new for the upcoming STS-11/41-B mission 
by mounting a glass plate between optics an arrays. 
However, the band still is slightly out of focus. 
During the Kenya data take as shown in this example 
M0MS-01 was operating in the lower gain mode of the 
two, which could be selected by the MOMS mission 
specialists at Johnson Space Flight Center in 
Houston. Thus the higher spatial resolution of 
MOMS versus TM is compensated by a lower dynamic 
range (see also Fig. 5). 
Complementary to the investigations of the working 
group at NASA/GSFC the data comparison was carried 
out at the AGF-Working Group Geoscientific Remote 
Sensing by employing the following approach: 
- display and visual comparison of MOMS 600 and 900 
nm bands and TM bands 2+3 (2+3 and average 
calculated) and 4, 
- MOMS 900/600 nm and TM 4/2+3 ratio processing and 
visual comparison, 
- MOMS and TM IHS (Intensity, Hue, Saturation) 
processing to generate color renditions (see Fig. 
7 and 8), 
- calculation of histograms (see Fig. 9), 
- calculation of scattergrams (see Fig. 10). 
Figures 7-10 show the results obtained in the 
testsite Atacama desert, Chile. 
Figure 7 and 8: MOMS and Thematic Mapper IHS 
proessing of a section of the testsite Atacama 
desert. MOMS and Thematic Mapper data have been 
treated with equal processing methods for comparing 
the system's performance for thematic mapping. 
Different colors of the same surface features are 
due to a different portioning and range of spectral 
bands (see also Fig. 5). MOMS features - as given 
by the specifications - a higher spatial resolu 
tion than TM, which in this specific example is 
not being compensated by a lower dynamic range, 
because MOMS was switched to gain level 2 (see 
also figures 9 and 10). The slight defocussing of 
the MOMS infrared band does not afreet the image 
quality as the resolution depends on the highest 
resolving data used within one processing, which 
is the 600 nm visible band. 
The sun azimuth angle between both scenes is 
nearly perpendicular, thus different geological 
features are enhanced. 
In the framework of the cooperative effort between 
NASA and BMFT MOMS'and Thematic Mapper's system 
performances have been compared in terms of spatial, 
spectral and radiometric resolving powers and noise 
characteristics by NASA. 
The evaluations at the AGF-Working Group Geoscienti- 
fic Remote Sensing were focussed on preparing 
application - oriented computer processings of 
both systems under equal conditions and comparing 
their applicability for thematic mapping. 
The results can be summarized as follows: 
- when operating in gain level 1, MOMS has a lower 
dynamic range then TM, whereas, when switched to 
gain 2, the dynamic ranges are comparable. 
- the computer processings prove MOMS to have a 
higher spatial resolution, when the exactly 
focussed visible band is used directly or 
processings including this band. The infrared 
band is out of focus, thus point spread function 
calculations indicate a lower spatial resolving 
power of MOMS versus TM. The spatial resolution 
of MOMS decreases from the left to the right 
side of one detector array. 
- the noise variances in both MOMS and TM are 
similar, but since MOMS is a 7-bit system the 
percentage of the image radiometric information 
containing noise is greater and the SNR of TM 
is higher. 
- the noise pattern in MOMS images has a vertical 
as well as a horizontal structure. The vertical 
structure is due to miscalibration of individual 
detectors and changing response across detector 
arrays. There is also a significant difference in 
noise variances between odd and even detectors. 
The absolute radiometric correction applied to 
the data for the recent evaluations at the AGF- 
Working Group improves the pixel grey value 
variation within one scan line of maximum 3-4 
in raw data to 1 - 2 as could be found by 
analyzing image profiles. 
- the geometry of the MOMS instrument was found to 
be very stable. Although geometrically corrected 
TM data has a pixel spacing of 28,5 meters, 
subsets of the TM images could be registered to 
the MOMS images with an average pixel error of 
10 meters. 
The results elaborated until now show the two 
instruments to be to a certain extend similar in 
the spectral bands that were compared. Although 
the MOMS scanner has a smaller IF0V, its lower 
modulation transfer function versus TM compensates 
this advantage especially surface features under 
low sun angles or low contrast phenomena have been 
observed with the instrument being switched to 
gain level 1. 
Operating in gain mode 2 an improvement in resolving 
power can be stated. 
The deficiencies are due to the CCD arrays used 
(Reticon CCPD 1728). 
For the upcoming M0MS-02 to be tested in space 
aboard the D-2 mission actual sensor developments 
will be used featuring more pixels per scan line and 
a better overall performance (see following chapter). 
Optoelectronic arrays have already been tested and 
evaluated concerning their applicability for space- 
borne remote sensing in the framework of a phase-B 
study on Stereo-MOMS, the operational representative 
of the MOMS family for the Polar Platform in the 
MOMS-02, as suggested for a space flight aboard the 
D-2 mission, will feature the following technical 
- three nadir looking multispectral bands (560 + 20

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