Re: Number of Observable Satellites

From: Frits Westra (
Date: Thu May 23 2002 - 08:58:13 EDT

  • Next message: Allen Thomson: "Re: Number of Observable Satellites"

    Hello David,
    A couple of weeks ago, I came across below "factfile" from ESA on the
    total number of objects in orbit.
     Frits Westra -- PE2ATC -- -- 52.22N 06.38E
    Original Date:    Mon,  6 May 2002 15:39:43 +0200 (CEST)
    ========================== Forwarded message begins ======================
       Space junk: A factfile
       PARIS (AFP) May 05, 2002
       Following are facts about orbiting space debris:
       - There are at least 100,000 and possibly more than 150,000 man-made
       objects in orbit, according to European Space Agency (ESA) estimates.
       Only between 600-700 objects are operational satellites and the
       International Space Station (ISS), which means the rest is junk.
       - The risk of collision with debris is statistically small, at between
       1-2 percent over a spacecraft spending five years in low Earth orbit.
       - The risk to people on the ground is negligible because debris that
       re-enters the Earth's atmosphere usually burns up completely.
       - Any orbital impact can be disastrous, however. A one-centimetre
       (half-inch) fragment, travelling at eight kilometers (five miles) per
       second, can release enough energy to destroy a 100-million-dollar
       satellite. A piece larger than two cms (one inch) could be enough to
       smash through the shielding of the ISS, causing its air to vaporise
       into space.
       - Only 8,700 objects in orbit are being systematically tracked, using
       ground-based radar and telescopes. These are objects that are the size
       of a tennis ball or larger.
       - The position of many smaller objects is known approximately, thanks
       to computer simulations made when for instance a rocket booster
       explodes. But many tiny fragments are impossible to locate or track
       accurately, which makes them very dangerous.
       - There are five international treaties on the use of space, but none
       applies specifically to debris. The UN next year may adopt guidelines
       under which countries launching satellites take steps to minimise the
       risk of debris, but these measures are unlikely to become
       international law.
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    On 23rd May 2002, wrote:
      >Date: Wed, 22 May 2002 16:53:28 -0700 
      >From: "David Dodge"<> 
      >Subject: Number of Observable Satellites 
      >If someone could provide me with a guesstimate of how many
      >satellites the average person can see from a mag 4 sky, an
      >idea of how many satellites reach 6 mag, and how many
      >satellites there are currently in orbit, I would be most
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