Page 165 - Intro to Space Sciences Spacecraft Applications

152 Introduction to Space Sciences and Spacecraft Applications
3. If the sensor in Exercise 2 is a 10 x 10 pixel array of CCDs generating
byte-sized words each sample, and the transmission rate is limited to
200 Mbps, determine the sensitivity of the system and the maximum
sampling frequency for the system.

4. A photographic reconnaissance satellite operates at an altitude of 150
km, always looking straight down. It has a lens with a diameter of 0.5
meters which projects the received images onto a 64 x 64 pixel array of
CCDs with a receiving capability from 5 x 1014 Hz to 6 x 1014 Hz (0.69
to 0.59 in wavelength where lfi = 1 micron = meter). Pulse code
modulation (PCM) is used to digitize the data, but the system is limit-
ed to 16 bits of information for each CCD each sample. Fifteen thou-
sand pictures are taken each second (for overlap). Determine the fol-
lowing:

a. The field of view of the image. Use the median wavelength of 0.555
for the calculation.
b. The number of quantization levels available.
c. The frequency sensitivity of the system.
d. Total number of bits produced each sample.

e. Transmission rate in Mbps.
f. (EXTRA CREDIT) If the CCD array is 1 square meter, what is the
image resolution of the system? (OR) Determine if the picture-taking
frequency is sufficient for image overlap.
5. A remote sensor has a 32 x 32 pixel array of infrared-sensitive charged-
couple devices (CCDs). The range of sensitivity for the CCDs is centered
between 250 OK and 500 OK. Pulse code modulation (PCM) is used to
digitize the data, and the sensitivity range has been divided into 16 quan-
tization levels. Sampling fiequency is 10 Khz.

a. What is the temperature sensitivity (represented by each Q-level)?
b. How many bits of information does a CCD produce each sample?
c. What is the total number of bits produced each sample by the array?
d. What is the transmission rate of the system in bits per second (bps)?
6. A passive remote sensor has a 1 meter diameter circular lens and oper-
ates at a frequency of 3 x lOI4 Hz. Calculate the IFOV at a range of
1,OOO km. What would be the ground IFOV if the grazing angle was
60°?