Slashdot Mirror
R.I.P. Iridium
Archeopteryx writes, "Motorola has posted a notice that they expect, barring a financial 'White Knight,' Iridium service to end at 11:59 p.m. EST on March 17.
A few questions come to mind: 1) What becomes of the abandoned satellites? They are a real nuisance to astronomers due to the 'Iridium Flash' effect, and they complicate launch windows for satellites destined for any inclination. 2) Have these any Ham Radio use? 3) Assuming there is a use for them, who owns them after they are abandoned? Any Space Law experts out there? An abandoned ship is subject to salvage laws; how about an abandoned spacecraft?"
A link from an old Slashdot story is a story in Wired. Basically, Iridium use(s|d) a frequency that "bled" into one frequently used by radio-astronomers to observe the cosmos.
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The Future: Some assembly required; batteries not included.
Iridium satellites have three large, flat, reflective antennas arrainged at an angle to the main spacecraft. These antennas, when at the right angle, can produce a very bright glint of reflected runlight. If you know where to look, the flares can be seen in broad daylight.
Look here: http://www2.satellite.eu.org/sa t/vsohp/iridium.html
They explain the effect, and even link to flare prediction software.
Specifically, the antennae on the Iridium are flat and highly polished surfaces. The flashes can get as bright as -8 magnitude for a few seconds.
The web page to check out is www.heavens-above.com. Give them your latitude and longitude, and they can provide you with predictions of where to look and when.
The frequencies were protected by international treaty. Additionally, MOT agreed to respect the critical frequencies when they received nearby frequencies. Later, they went back on their word and ignored the international treaty.
In fairnes to MOT, they have worked with the major radio astronomy facilities to avoid making the frequency completely useless by scheduling windows when they would significanly limit their interference in certain locations. However, they still interfere and it makes scheduling time an even for obnoxious task for astronomers who try to maximize the utility of their observatories.
Even worse, it sets a very bad precedent for a big company to threaten to ruin an important scientific resource, and then "be nice" by being better than originally planned. What if every big company decides to put up a big network of satelites interfering with one frequency range, but agrees to be nice in certain locations at certain times? Not good for science!
Someone was interested in Ham Radio use of the sats (like the Phase 3D or Oscars). There's a lot of them up there (66 Iridium sats), but they're out of frequency. Also, they're right in the LEOsat hotspots for spectrum use, so I don't doubt that they'll re-farm them out or resell them.
Satellites: 66
Orbital Planes: 6
Orbit Height: 780 km (these are LEOsats)
Inclination of Orbital Planes: 86.4
Orbital Period: 100 min. 28 sec.
Lifetime: 5 to 8 years
Frequencies and Rates
Telephone and Messaging Service Links are 1616 - 1626.5 MHz (L-Band)
Intersatellite Links are 23.18 - 23.38 GHz (Ka-Band)
Ground Segment Links:
Downlinks: 19.4 - 19.6 GHz (Ka-Band)
Uplinks: 29.1-29.3 GHz (Ka-Band)
Digital Voice, Fax, and Data are transmitted at 2.4 Kbps
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