[PLUG-TALK] Micro satellites?

[Keith Lofstrom]

On Tue, Mar 08, 2016 at 11:02:12AM -0800, Mel Andres wrote:
> https://www.facebook.com/DiscoveryNews/videos/10153789288023387/?fref=nf
> 
> Wonder where they came up with this?

The "idea" of small nonsteerable communication satellites
has been around a long time.  The confusing idea of naming
a 10 to 100 kilogram satellite a "microsatellite" also
needs to die.  What they illustrate is a 3U cubesat -
4 kilograms - typically called by the confusing name of
"nanosatellite", 1 to 10 kilograms.

Since these can't steer, I call them "projectiles". 
The parabolic reflector deploying like a parachute
is an amusing touch, though impossible as shown, but
illustrates an important point: without a source of
thrust, drag will decay the orbit for this satellite
pretty fast.  It will not last more than a year or
two, and while it does, it will be a collision
hazard for other satellites.

These are shown deploying at low speed from one dispenser.
Which means they are all in pretty much the same orbit.
That's pointless.  Actual global satellite constellations,
like Iridium or GPS, are all very separated, in highly
inclined (tilted to the equator) orbits, which means they
are visible far to the north and south.  They are also
separated in position around the orbit (mean anomaly), and
the inclined orbits cross the equator in different places
(ascending node).  The velocity differences between the
different orbits thousands of kilometers per second, and
can be more than the initial orbital velocity.

Satellites in high circular equatorial orbits can't
see the north and south poles, but they can see a band
around the equator.  The "O3B" satellites orbit 8080
kilometers above the equator, and can be seen by a
15 degree elevated ground antenna up to 50 degrees
north (and south), around the Canadian border. 

Geostationary satellites orbit 35770 kilometers above
the equator, and can be seen up to 67 degrees north
with a ground antenna also pointing 15 degrees above
the southern horizon.  The geostationary orbit is full
of satellites spaced 1 degree apart, orbital slots
worth billions of dollars.  Cubesats and other
uncontrolled projectiles are NOT welcome there.

I work on Server Sky, http://server-sky.com .  These
will be 5 gram satellites half the size of a sheet of
copy paper.  They /can/ maneuver.  They will deploy at
6410 kilometers altitude above the equator, below O3B,
by the billions someday.  They will be visible up to 45 
degrees north, delivering internet services to tropical
developing countries.  Also useful for short wavelength
radar, tracking uncontrolled projectiles like cubesats.

What concerns me most about projects like this is that
they mislead the public.  Space has physical and legal
rules, which they seem to ignore.  They may gather some
investment money, and fail, which will make it harder
for legitimate projects to succeed, perhaps causing new
laws to be passed against all small satellite projects.

Ah well.  You can fool some of the public all of the
time ...

Keith

-- 
Keith Lofstrom          keithl at keithl.com