Project Starshine is a
voluntary group supported by the
US Naval Research Laboratory, the
Space Grant Program, and
NASA. It's purpose is to learn about the outer
layers of the
Earth's atmosphere, how it changes and how those changes effect
orbiting objects. The Project Director is Prof.
R. Gilbert Moore
The Starshine
satellites look like large
disco balls initially
orbiting 470
km above the
Earth in a region of the atmosphere known as the
thermosphere. The
International Space Station, the
Space Shuttle and many other satellites
orbit at the same height as the Starshine satellites.
Starshine 1 was launched on
June 5th 1999 and dropped out of orbit on
Feb. 18th 2000 . Starshines 2 and 3 are still up there
now, 3 was launched on
Sept. 29th 2001, and 2 was launched on
Dec. 5th, 2001 - they're numbered in the order which production started rather than the order in which they were launched. Starshines 4 and 5 are set to be launched simultaneously in January 2003.
The satellites are
spheres made of
aluminium and are covered in flat
mirrors. These mirrors
reflectspacesunlight back to Earth and allow us to see them with the
naked eye. Seen from Earth, they have the same
brightness as
1st magnitude stars but
pulse gently as they rotate. The mirrors were
polished by groups of
students from around the world in a
collaborative project. Starshine 2 has 845 mirrors which were polished by 30,000 students from 26 different countries. Starshine 3 took 40,000 students to finish its 1500 mirrors. Lots of flat mirrors are much easier and cheaper to make and polish than one big spherical one. This is why the Starshines look the way they do.
The
price of putting things into orbit is calculated by
volume and
weight and is one of the two main reasons why the starshine satellites are made primarily of aluminium. The other reason is
insurance. They would need a $100,000,000 insurance policy with a $50,000
premium if any part of them was likely to survive
reentry and fall to the surface of the earth. Starshine 1 was completely
vaporised about 80 km up.
The
air in the thermosphere is very thin but still enough to cause mild
resistance. This is all part of the project. Each of the satellites loses a few meters of altitude for every orbit of the Earth as does the International Space Station - ISS however has
boosters which prevent it from
falling back to earth. Not so Project Starshine's
birds,
atmospheric resistance is part of the reason they're up there
Observers on Earth first calculate their exact position on the planet then
precisely record the
position and
times of the satellites as they pass known
stars. By entering these figures into the project's
website, details of the satellites' orbits can be calculated using
equations originally derived by
Pierre Laplace. These orbits change as the
density of the thermosphere changes.
The thermosphere and indeed the entire atmosphere regularly fluctuates in size, shape and density. This is caused by
solar activity. Another layer of our atmosphere called the
magnetosphere is formed by the
interaction of the
Earth's magnetic field and the
solar wind and the
Sun's
interplanetary magnetic field. Seen from side on, the magnetosphere looks like the ripples around a stone in flowing water. When there is a
Coronal Mass Ejection or
solar flare, the solar wind increases and the magnetosphere is deformed, taking the rest of the atmosphere with it.
Until now, we did not have a good understanding of how this solar activity affected atmospheric density. Now we can see
CMEs coming thanks to the
SOHO satellite which permanently watches the Sun and we can find out the effect they have on the atmosphere thanks to the Starshine satellites.
To find out more about the project, visit it's homepage at www.azinet.com/starshine
The starshine satellites are visible from most parts of the Earth at some time. To find out when where to look for these and other satellites from your current location, visit www.heavens-above.com
Other sources - www.spaceweather.com, www.nasa.gov
---------
Additional - 26/4/2002
Starshine 2's orbit is now in the final stages of decay. It is set to re-enter the Earth's atmosphere some time today. This is about a month or two earlier than predicted because of recent high levels of solar activity. For re-entry times on this and other starshine satellites, you can visit :
http://www.azinet.com/starshine/starshine_reentry.html