# Math Help - Determine orbital period

1. ## Determine orbital period

Hi there

I'm hoping somebody can give me a hand with a problem I'm struggling with. The problem gives the height of a satellite at its perigee (181km) and its apogee (327km), the average earth radius (6371km) and that the "period of a low-orbit satellite is 84min". It then asks me to find the orbital period of the spacecraft.

I presume this involves Keplar's laws, the mention of the apogee and perigee make me suspect this involves the third law (which states that the square of the orbital period is proportional to the cube of the major axis), other than this I really don't know how to approach this problem. Any help would me much appreciated.

Cheers

2. Originally Posted by zcus05
Hi there

I'm hoping somebody can give me a hand with a problem I'm struggling with. The problem gives the height of a satellite at its perigee (181km) and its apogee (327km), the average earth radius (6371km) and that the "period of a low-orbit satellite is 84min". It then asks me to find the orbital period of the spacecraft.

I presume this involves Keplar's laws, the mention of the apogee and perigee make me suspect this involves the third law (which states that the square of the orbital period is proportional to the cube of the major axis), other than this I really don't know how to approach this problem. Any help would me much appreciated.

Cheers
I think you are to assume that the orbital period of a circular orbit of radius 6371 km is 84 min. This gives you a reference orbit so you can now use Kepler's third law.

CB

3. Thanks, I think I got it now