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Compute F-number of optics, Fit

F#= VD

F#= 2.7

Typical range = 4-6

Compute field of view of optical system, FOV

FOV= IFOV• Nm

FOV= 0.628 deg

FOV tor the array of pixels

Determine cut-off frequency, Fc

Fc = D/A/J

Fc =0.09 line pairs/m

Referred to nadir

Determine cross-trad« Nyquist frequency, Fm

0.017 Ip/m

Referred to ground pixel resolution at nadir

Determine along-track Nyquist frequency, Fm

0.017 Ip/m

Referred to ground pixel resolution at nadir

Compute relative Nyquist frequencies,

FqcOMlFqa

r - ^nc . c -ña rqc —p-• r<P —p-•c rc

= 19%

% of the cutoff frequency used for this case

Find optics PSF as a function of distance, r, from center of detector

PSF(r) = [A J-) (2)/2p ZawrD/Af

See Figs. 9-26A and B

Use -2d< r< 2d J-i is the Bessel function of order 1

Find optical modulation transferfunction (MTFq) for dear circular optics

I2 fJi-c2 J

See Rg. 9-26B Use 0 S FS Fc CaF/Fc

Step 6. Estimate Sensor Radlometry (for Nadir Viewing)

Compute detector MTF MTFx=[sSn(ly)/fy? cross-track, MTFX,and M7Fy= \s\n(Fy)/Fy I along-track, MTFy

Fx^nXF

Fyajl/F

Compute system MTF cross-track, MTFa

MTF3(F) = MTf\){F) • MTFC(F)

See Rg. 9-22

Let Frange: 0 <.F<.FC

Define equivalent blackbody temp. T

Design parameter

T = 290 K

Blackbody temperature of the Earth

Define the operating bandwidth, AA

Design parameter

AA= 1.9 pm

Based on subject trades

Determine blackbody spectral radiance, Lj,

La=B(A)/4h fi[A) from Eq. (9-2)

0 0

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