A sphere with a 40,000 km circumference has an area of
50,929,581,789,406,507 square decimeters. A decimeter is 1/10th meter
- roughly 4 inches in length.
http://www.ee.washington.edu/consele.../hdtv/95x5.htm
HDTV standards are 1080 x 1920 pixels updated 60x per second - that's
124.4 million pixels per second. At 6 km/sec flyover speed the
spacecraft moves 100 meters, or 1,000 decimeters, per frame. Which
might be convenient. A single HDTV sensor, at 1 decimeter resolution
would 'paint' a frame 108 meters by 192 meters on the ground. Every
second each sensor would pick up to decimeter resolution an area 192
meters by 6 kilometers. 10 HDTV cameras per satellite stacked side by
side would pick up to decimeter resolution would cover a swath 1.92 km
wide by 6 kilometers long every second. In s833 econds the 1.92 mile
wide swath would be 5,000 kilometers long. Eight satellites in the
same orbit following one another would image a 1.92 km wide strip every
833 seconds (13.89 minutes)
The Earth rotates 385.8 kilometers at the equator every 833 seconds.
And the eight satellites picked up a strip only 1.92 kilometers wide
with its 10 HDTV cameras. That's only 1/200th the total width. And
its less than 1/20,000th the circumference of the Earth. If we had a
string of 2,010 HDTV cameras in a string of lenses we cpi;d cover the
entire 385.8 km wide strip. This lens array needn't be too big. The
Rayleigh limit means your lenses ahve to be around 6 cm across, at an
altitude where you move over the ground at 6 km/sec. A planar array of
appropriately shaped lenses could provide the needed resolution and be
only 3 meters x 3 meters -10 ft by 10 ft - to use 2,010 HDTV CCDs to
image a region 385.8 kilometers across and 108 meters tall - to a
decimeter resolution per frame. The lenses aren't in a string, they're
in an array, with each strip in the array pointing a little to the left
or right of the previous strip. Fresnel lenses would be very
lightweight despite their area.
Thus, eight satellites in a polar orbit would provide continuous
coverage of the Earth to a decimeter resolution, and complete a scan of
the entire Earth to this resolution every 12 hours.
A collection of 192 satellites in 24 polar orbital planes, would
provide half-hour updates of the surface to this resolution.
The 192 satellites would also provide a two-way wireless
telecommunications capability to the surface via phased array microwave
antennae capable of painting a large number of stationary cells on the
Earth's surface below.
The satellites too would have a 50 Terabit/second open optical telecom
capability using a multi-spectral laser system with a low power
telescop (like a questar) Six questar type telescopes with 2 axis
pointing capabilities would be capable of connecting with the nearest
neighbor - the one ahead in the ring, the one behind in the ring, and
with two nearest neighbors on adjacent rings.
Within each satellite is an image storage and retrieval facility, along
with a massive router capable of communicating with nearest neighbor
sats. GPS data is used along with a cell map of the Earth's surface,
to maintain a fixed doppler corrected cell via microwave from the
moving collections of satellites overhead using their phased array
capabilities.
Thus 192 satellites could simultaneously provide global wireless
telecom capabilities along with a live picture of Earth - akin to
Google Earth - to 4 inch resolution - updated every half hour. Imagery
could be stored on board the satellite network, and combined to create
a best available image, so clouds for example could be eliminated by
recognizing them and subtracting them from images that are then
combined to produce cloud free images.
Also, the phased array telecom system could work in side scanning radar
mode - providing a high resolution microwave image of Earth as well,
data which could be added to the other data streams available to the
network. This could provide ranging data that is converted to
elevation data. Changes in elevation could be mapped this way, which
might be interesting.
And, the phased array antennae system could provide timed signals for
an alternative to the naval GPS system - and likely be superior due to
their greater number, lower altitude and superior signal timing.
192 satellites provide global coverage to decimeter resolution every
half hour, provide broadband wireless telecommunications throughout the
world.
Osmium, Platinum, and Iridium have isotopes with atomic weights of 192
- there is no naturally occuring element with an atomic NUMBER of 192.
The original Iridium system was to have 77 satellites. Maybe this
revised Iridium system could have the same name since the atomic weight
of an isotope of Iridium has the same value as the number of satellites
proposed here! lol.