This post is part of a series on understanding the meaning behind the values contained in a Two Line Element set, or Keplerian Elements. The main article is here.

International Designator (Piece)

This is a 3 letter code to designate the individual pieces from a successful launch.
The first code is A, the 26th is Z, the 27th is AA and so forth.
(more…)

This post is part of a series on understanding the meaning behind the values contained in a Two Line Element set, or Keplerian Elements. The main article is here.

International Designator (Launch Number)

This is a three digit number showing launch number for the year. These numbers are designated by the World Warning Agency (WWAS).

In most cases, the first launch of the year is numbered 001 and then incremented sequentially until the last launch of the year.

This post is part of a series on understanding the meaning behind the values contained in a Two Line Element set, or Keplerian Elements. The main article is here.

International Designator (Year)

This is a two digit number showing the year of the launch.

Values between 57 and 99 are for the years 1957 to 1999 while values between 00 and 56 are for 2000 through to 2056 (This range is used as the first satellite, Sputnik 1 was launched in 1957).

This post is part of a series on understanding the meaning behind the values contained in a Two Line Element set, or Keplerian Elements. The main article is here.

Classification

This is a one character string designating the classification of the satellite.

Known values are:
C – Classified
U – Unclassified

There may be others however public lists only show satellites classified as “U”.

This post is part of a series on understanding the meaning behind the values contained in a Two Line Element set, or Keplerian Elements. The main article is here.

Satellite Number

This is a distinct incremental value is a assigned to each new orbital object. Officially, it is known as the “Satellite Catalog Number”. NORAD started the counting at 1 and USSPACECOM who are now in charge of the numbering, have continued it.

The number is only used once, even if a satellite decays (re-enters the atmosphere).

This value can be up to 5 characters in length. As of recent, the number is up to 34540.

Notable examples:

25544 - International Space Station
20580 - Hubble Space Telescope
00001 - Sputnik 1 Launch Vehicle (decayed)

This post is part of a series on understanding the meaning behind the values contained in a Two Line Element set, or Keplerian Elements. The main article is here.

Line Number

Did you really need detail on this one?

This is the line number of the data. As the data is supplied in two lines, this value can either be 1 or 2. The title line (in three line sets) does not have a line number.

Examples:

1
2

This post is part of a series on understanding the meaning behind the values contained in a Two Line Element set, or Keplerian Elements. The main article is here.

Satellite Name

Did you really need detail on this one?

This is simply the common name of the satellite. It can be up to 24 characters long.

Examples:

VANGUARD 1
DELTA 1 R/B
FENGYUN 1C DEB
ISS (ZARYA)
ISS DEB (TOOL BAG)
IRIDIUM 33 DEB

Just a few minutes ago, the crew of the International Space Station were evacuated to a Soyuz capsule (for possible emergency reentry back to earth) due to the risk of a piece of orbital debris striking the station.

The correct story involves a piece of debris around 1/3 of an inch (8mm) in size travelling at high speed. The piece was predicted to pass within 3 miles (5km) of the space station and was considered to have a low risk of collision (but still a risk). The THREE man crew spent 11 minutes in a Soyuz escape capsule just in case the station was hit. The debris was detected too late for the space station to perform a collision avoidance maneuver (these are normally done days in advance).

Two two objects involved were ISS (Norad ID 25544) and PAM-D DEB (Norad ID 25090). The orbital separation (the distance between each orbit) of the two objects was 2km and the closest point between them was 8.8km. Note that the space station is traveling around 7.5km per second and these distances were calculated from data supplied by NORAD. At their combined speed, there was only 0.5 seconds separation.

Check out how the story has been reported around the world:
The crew of the international space station survived a close call with space junk Thursday.

http://www.thesun.co.uk/sol/homepage/news/article2316065.ece
Large chunks (plural) of debris??
“..ASTRONAUTS fled their space station today fearing it could be crushed by large chunks of space debris. Nasa officials said the scrap is large enough to cause significant damage to the International Space Station..”

http://www.postchronicle.com/news/original/article_212214695.shtml
Eighteen member crew?? – It’s actually 3 members of the Expedition 18 crew.
“..NASA has revealed that the eighteen-member crew at the International Space Station has been evacuated from the ISS due to precautionary measures…”

http://www.wfaa.com/sharedcontent/dws/wfaa/latestnews/stories/wfaa090312_wz_spacedebris.2a8dceb8.html
Two member crew??
“..NASA says the two-person crew aboard the International Space Station took shelter in an escape capsule after some space debris was predicted to come dangerously close to the orbiting laboratory. ..”

http://www.news24.com/News24/Technology/News/0,,2-13-1443_2484541,00.html
A cloud of debris??
“..The crew of the International Space Station on Thursday entered its Soyuz capsule to prepare for evacuation in case of a collision with a debris cloud, Nasa said…”

http://www.chron.com/disp/story.mpl/front/6307525.html
4 inch long debris?
“..The debris, about 4 inches long, whizzed within three miles of the orbital outpost at 11:39 a.m., CDT, causing no damage…”

http://scienceblogs.com/authority/2009/03/debris_threat_to_international.php
How large is moderately large?
“..A moderately large piece of space debris has only recently been identified as a threat to the International Space Station – too recently for the station to be moved out of the way. The object is now projected to pass close enough to the ISS to put it into the high threat category…”

After posting my kmz file of the Satellite Collision Debris, Tom Wagner of Iowa turned it into a 3D image.

The picture has been published on spaceweather.com.

Here is the image (links to spaceweather.com post).

(This page is a work in progress. It will be complete once all of the individual values are described in full.)

The orbital elements of the satellites tracked by NORAD are supplied in a “Two Line Element” format. This data is sometimes referred to as “Keplerian Elements”.

Here is a sample for the International Space Station for today.

ISS (ZARYA)
1 25544U 98067A   09070.38837942  .00007697  00000-0  63677-4 0  4357
2 25544  51.6394  87.9530 0009582 111.8389  22.9968 15.71382598590567

My intention with this post is to not just tell you what each value is, but demonstrate exactly what they relate to. Click on the description field for an in-depth detailed description.

Title Line

Line 1

Line 2