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## Homework Statement

A remote sensing satellite is deployed in a circular sun-synchronous orbit with inclination 96.85 degrees.

A. Calculate orbit altitude. I did this and got 349km.

B. The spacecraft coefficient is 200 kg/m^2. Solar conditions during the spacecraft launch are characterized by the solar flux F10.7 = 90. Is the orbit altitude sufficiently high for the spacecraft to operate through the estimated 2-year life time? What would be the spacecraft approximate lifetime if it is launched during solar maximum?

C. What is the maximum distance from the spacecraft to the horizon? I got 2139 km.

D. What is the maximum possible swath width? I got 12094 km.

E. What is the maximum possible time in view? I got 1560 seconds.

F. What is the ground speed of the subsatellite point? I got 7.3 km/s

G. The ground communications station is located at the satellite ground track. What is the communication time if the local conditions limit spacecraft visibility to elevation angles larger than 18 degrees?

## The Attempt at a Solution

Assuming I got A,C,D,E,and F correct, I need help with B and G. For part B, I know the solar flux is related to the atmospheric density. If i get the atmospheric density I can use that, the radius of orbit and the ballistic coefficient to calculate the change in radius per revolution, and can calculate # of revs in a given time period since I know orbital velocity. I just don't know how to find the atmospheric density, rho, in the equation below which relates what I just talked about..

delta R(per rev) = -2*pi*(1/ballistic coeff)*rho*R^2

For part G, I have no clue where to start or what to do.