HR c folct orc a PIE AA 7) cime ace ET EU ENT S = —M— uu R » 2 
j = A ACT BB AREE a t PACE NE TR a PS SERRE Va PEN eT APN a RE gb bi 
^ 
CUSCO VEN I TERETE 
Here, R : radius of Earth (km) 
: swath width (km), here assumed as 105 km 
required integration time, here assumed 104sec minimum 
: period of satellite (sec) 
IFOV (m) 
e 53590 
We can realize that such system needs 12 sensor elements (for example 
photomultiplier) at least for each band, if we require 45 meters IFOV 
at ground. This will be result in 48 sensor elements totally and 
increases in weight and volume of system. 
Thus, if we want to meet the requirement of 10 meter IFOV(see Table 
1), we must to adopt some other scanning system. Electronic self-scan- 
ning radiometer will be the most hopefull system to meet such high reso- 
lution requirements. This concept will be used in the HRV(High Resolu- : 
tion Visible) of SPOT project in France and in the HRPI(High Resolution (» (4 
Pointable Imager) in U.S.A.. The Japanese first earth observation 
satellite MOS-1 will use also this concept in the scanner system, and 
it will be called as MESSR(Multispectral Electronic Self-Scanning 
Radiometer). 
In Table 2 shown a general comparison between mechanical scanner and 
electronic self-scanning radiometer. 
2. A performance evalutaion formula of electronic 
self-scanning radiometer 
The signal to noise ratio of video signal at the sensor out put is 
given by following equation. 
(9), — 4 NA (1- YT IM CTFRMTE Tle @ 
4 Fr NES 
6 9 
Here, (S/N) : signal to noise ratio at a given spectral band 
Na : radiance at the optics aperture within a given spectral 
band 
Fac : speed of optics 
> : optics obscuration 
Ta : optics transmission 
YA : relative response of sensor element 
(OTF), : OTF of optics at & given spectral band 
(MIT) : MTF of sensor array at a given spectral band 
T : integration time 
NES : noise equivalent signal 
The MTF characteristic of sensor array depends on a irradiated wave 
length and the aperture pattern. Fig. 2 shows the ideal aperture