## Y X Y

where 7} is the maximum look angle in radians, h is the orbit altitude, Vg is the spacecraft ground-track velocity, Sw is the swath width, X is the across-track pixel dimension, and Y is the along-track pixel dimension. The approximation is good for small swath widths. The data rate can be increased by transmission overhead such as housekeeping data or coding and it can be decreased by data compression. (See Sees. 2.1.1, 13.2.2, and 15.3.2.).

 Step Calculation FireSat Comments Step 1. Define Orbit Parameters Define orbital altitude, h Design parametert h = 700 km See Table 3-4, Sec. 7.4 Compute orbit period, P Eq. (7-7), IRC P= 98.8 mln Assumes circular orbft Compute ground track velocity, Vg Eq. (5-31), IRC* Vg = 6.76 km/s Assumes circular orbit Compute node shift, AL Eq. (7-13), IRC* Ai = 24.8 deg Function of Inclination Step 2. Define Sensor Viewing Parameters Compute angular radius of the Earth, p Eq. (5-15), IRC* p = 64.3 deg Depends on orbital altitude Compute max distance to the horizon, Dmax Eq. (5-17), IRC* 3,069 km Depends on orbital altitude Define max. Incidence ang. M, or max. Earth cen. ang. ECA^ Design parameter, IRC* IA = 70 deg Adjust swath width for good coverage (Sec. 7.4) Compute sensor look angle (= nadir angle), n Eqs. (5-24) or (5-25b), IRC* »1 = 57.9 deg Will be less than p Compute mln. elev. angle, e= 90°- IA Eqs. (5-25b) and (5-28), IRC* e=20 deg If max. ECAmgx given, compute e Compute max Earth central angle, ECA^ Eqs. (5-25b) and (5-26), IRC* ECAmw(= 12.1 deg If e given, compute ECAna* Compute slant range, R§ Eq. (5-27), IRC* f?s = 1,578 km Rs here = Din Chap. 5 Find swath width = 2 ECAmax 2 ECAmax= 24.2 deg Determines coverage Step 3. Define Pixel Parameters and Data Rate Specify max. along-track ground sampling dlst, /ma* Design parameter Ymax= 68 m Based on spatial resolution requirements atEGV, Determine Instantaneous field of view, IFOV ¡rov _ Ynwx 180deg Rs n IFOV= 0.00245 deg One pixel width Find max. cross-track pixel resolution, Xm^ at ECA^
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