•Use the “synodic” period of Mars to find its “sidereal”
period
–Synodic
period:
Time it takes Earth to “lap” Mars as both orbit Sun.
•This is the time between Mars “oppositions as seen from
Earth.
•780 days, or a little over 2 years
–Sidereal
period: Time it takes Mars to orbit Sun = 1 Mars Year
•1/P = 1/E – 1/S
= 1/365 days – 1/780 days =
1/687 days
•
•Collect pairs of Mars observations taken 1 Mars year
(687 days) apart
•
•For these
pairs of observations Mars will be in the same place in its orbit
•Earth will
be in a different place – allowing triangulation