Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Selection of bands for a newly developed Multispectral Airborne 
Reference-aided Calibrated Scanner (MARCS) 
M. A. Mulders 
Agricultural University Wageningen, Netherlands 
K.Schurer 
TFDL Wageningen, Netherlands 
A.N.de Jong 
TNO, Physics and Electronics Lab., The Hague, Netherlands 
D.de Hoop 
ITC, Enschede, Netherlands 
SUMMARY: A 16 band scanner is constructed which contains besides an array of detectors for measurement of 
radiation reflected and emitted from the land surface, the following: 
- a reference sensor which measures the flux of radiation coming from above from sun and sky; 
- a device for internal calibration of the signals derived from below of reflected and emitted radiation of 
the land surface. 
Further characteristics of the scanning device: 
- Silicon, Germanium, Leadsulfide, Leadselenide and pyroelectric detectors; 
- recording of data with videorecorders; 
- total scan angle of 60 degrees; 
- ground resolution at flying height of 500 m about 4.2 x 4.2 m . 
A number of bands is selected for this scanner. The bands have a width between 50 nm and 150 nm in the 0.3- 
3 pm range but become broader in the 3-10 pm range (width 700-1000 nm). An additional band is chosen around 
10.5 pm with a width of 5000 nm. The choice of bands is directed by the possibilities in the 0.3-13 pm range 
of the electromagnetic spectrum regarding information potential and transmission properties of the atmosphere. 
Indications may be obtained a.o. about the presence of iron oxides, lime, gypsum, layer silicates, soil 
moisture and about the coverage and condition of vegetation. 
INTRODUCTION 
Challenged by the high potential of multispectral 
remote sensing techniques for inventory of arid and 
semi-arid environments, the feasibility of a 
multiband instrument for earth-observation from the 
air was considered. As a result, a new airborne 
scanning device is being developed by the Physics 
and Electronics Laboratory T.N.O. (FEL-TNO, Den 
Haag), ITC (International Institute for Aerospace 
Survey and Earth Sciences, Enschede) and TFDL 
(Technical and Physical Engineering Service, 
Wageningen). The device should have a light weight 
enabling its use in the field as well. 
The original set of bands suggested by the first 
author (AUW, Agricultural University, Wageningen) 
covered the visible and near infrared. T.N.O. 
proposed bands in the extension of these zones into 
the ultraviolet and mid up to thermal infrared. 
The scanner may be expected to be completed at 
the end of 1986. The first test flights were made 
in April 1986 with the aircraft of the ITC (PHITC 
Piper Chieftain). 
MARCS 
MARCS is an acronym for Multispectral Airborne 
Reference-aided Calibrated Scanner. The scanner 
operates in 16 channels covering the range from 
ultraviolet up to thermal infrared. It has an IFOV 
of 0.5° x 0.5°, thus reaching a ground resolution 
of 4.2 m x 4.2 m from an altitude of 500 m. The 
scan width is 60°. In Fig. 1, a schematic 
presentation is given of its design. 
Use is made of a rotating mirror with a square 
cross-section. Four scans are performed on each 
full rotation of the mirror axis. In each scan 16 
picture-lines are recorded simultaneously for each 
of the bands. Thus, with an interval time between 
scans of 1.2 s, a groundspeed of 56 m/s results in 
a continuous recording of the scene under survey. 
Choppers are placed in front of each array for 
modulation of the incoming radiation flux and 
clamping purposes. 
Furthermore, internal calibration signals are 
measured 
in the dead 
time 
between 
two scans. 
By using interference 
filters 
and appropriate 
detector 
arrays, the 
following wavelength bands are 
taken for 
measurement 
: 
band 
centre 
width 
detectors 
(nm) 
(nm) 
1 
355 
90 
2 
485 
70 
3 
555 
50 
4 
605 
50 
Si 
5 
655 
50 
6 
800 
100 
7 
870 
60 
8 
1050 
100 
9 
1640 
80 
Ge 
10 
1750 
60 
11 
2175 
150 
PbS 
12 
2350 
60 
13 
3750 
700 
PbSe 
14 
4850 
700 
15 
9500 
1000 
pyro-electrical 
16 
10500 
5000 
material 
For measurement of the incoming radiation, a 
reference sensor is mounted on top of the aircraft. 
This sensor uses the same bands as described for 
the scanner and is developed by T.F.D.L. The 
detectors have diffusing entrance windows to 
closely approximate true cosine responses. Data are 
recorded during the scan. They are merged into the 
main data stream. 
The very high amount of data requires specific 
techniques for recording. For this purpose, T.N.O. 
and ITC have developed a system using 
videorecorders with digital data storage. For 
analysis of the recorded data, ground systems 
connected to large computers are available. By