On Monday, June 3, 1996 12:30:00 PM UTC+5:30, Frank Crary wrote:
In article , Pat wrote:
...the reason i heard sun synchonicity
was desired was not measuring building heights (which can be measured
at any time of day given the known sun angle, but rather to minimize
shadow changes in the photo so as to maximize photo-analysts chances
of spotting new construction or new building features.

I disagree. You can not do equally good height measurements at
any time of day. What's the length of a shadow at noon, on
the equator, on June 21? You'd need very good resolution to
measure the length of a nonexistent shadow... To get an
accurate measurement of height, you need shadows that are
much longer than the resolution of the image. How much
longer depends on the desired accuracy, but longer
shadows certainly help and that is a motive for sun-synchronous
orbits with early morning passes. As Henry pointed out, it
isn't the only reason as far as the Earth is concerned. I
guess I'm too used to thinking of observations of other planets...

Frank Crary
CU Boulder
hye,
I was reading about sun synchronous orbits and i had a lot of confusion reg
arding that topics so i was looking into various group pages which discusse
d this topic.I was wondering if a satellite is in sun synchronous orbit and
if it completes 14 orbits per day then will the satellite be passing over
one particular location on the earth twice a day.ie 7 am in morning and 7 p
m at evening or will it pass over one location on the earth only once.
The inclination of the orbit can be taken as around 98 degrees and time per
iod as 101 minutes.Altitude will be around 800 kms.
Please help if possible