Education
LessonSecondary school and early undergraduate (ages 14+) · 45 min

Understanding NORAD and COSPAR Identifiers

Every tracked object carries two names: a NORAD catalog number and a COSPAR International Designator. This lesson teaches students to read both, and to see why one encodes a launch and the other does not.

identifierscatalogsnoradcosparmetadata
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You may print and copy this lesson for one classroom or one family, for as many years as you teach it. You may not resell it or post the file publicly.

Overview

Ask a class to name a satellite and most will say "the ISS" or "Hubble". Those are nicknames. To track tens of thousands of objects without confusion, catalogs give every object a precise identifier, in fact two of them, assigned by two different systems for two different reasons.

The NORAD catalog number (also called the Satellite Catalog Number, or SATCAT) is a plain sequential integer assigned by the US Space Force as objects are catalogued. A lower number usually means an object was catalogued earlier. It says nothing, by itself, about which launch an object came from.

The COSPAR International Designator (the international standard, maintained through the UN-affiliated COSPAR/World Data Center system) instead encodes the launch: the year, the sequential launch of that year, and a letter for each separately-tracked piece from that launch. Two payloads on the same rocket share the year and launch number but get different piece letters.

At a glance

Learning objectives

  • Read a NORAD catalog number and explain what it does and does not tell you.
  • Decode a COSPAR International Designator into launch year, launch of that year, and piece.
  • Explain why two objects from the same launch share a COSPAR year/number but differ in the final piece letter.
  • Look up any satellite on OrbitalWiki and cross-check its two identifiers against a primary source.

Prerequisites

  • Comfort reading a table of numbers and dates.
  • No orbital-mechanics background required.

Required software

  • A web browser (to use orbitalwiki.com).
  • A spreadsheet application (Excel, Google Sheets, or LibreOffice Calc) to open the worksheet CSV.

Dataset version

OrbitalWiki live catalog. Record the dataset-release label from /datasets when available, or the exact access date for a live lookup.

Student materials

Student worksheet (7 satellites, blanks to fill in)CSV, opens in any spreadsheet app
Download

Student instructions

  1. 1Open the worksheet CSV. It lists seven real satellites by nickname, with the NORAD number and COSPAR designator columns partly blank.
  2. 2For each satellite, search its nickname on orbitalwiki.com (for example "Hubble" or "Landsat 8") and open its record page.
  3. 3Copy the NORAD catalog number and the COSPAR International Designator from the record into the worksheet.
  4. 4In the "launch year" column, decode the launch year from the COSPAR designator only (the first four characters), not from the launch-date field.
  5. 5Answer the two reasoning questions at the bottom of the worksheet: (a) which satellite has the lowest NORAD number, and what does that suggest? (b) Terra, Aqua, Landsat 8, Sentinel-2A and NOAA 20 are all Earth-observation satellites in similar orbits, do their identifiers show any relationship? Explain.

Expected output

  • A completed worksheet with the correct NORAD number and COSPAR designator for all seven satellites.
  • A correct decoded launch year for each, taken from the COSPAR designator.
  • A short written answer recognising that the lowest NORAD number (Hubble, 20580) reflects earlier cataloguing, and that the Earth-observation satellites do NOT share a COSPAR launch because they launched separately, in different years, a common and instructive misconception.
[teacher]

Teacher materials, not student-facing

Teacher answer keyCSV, verified against the live catalog
Download

Teaching notes

  • The key conceptual target is that NORAD number ordering ≈ cataloguing order (roughly time order), while COSPAR encodes the launch event. Students frequently assume the two must agree or that "similar satellites" share an identifier root; the Earth-observation set is chosen specifically to break that assumption.
  • Hubble (NORAD 20580, launched 1990) has a lower NORAD number than the ISS (25544, launched 1998), which matches launch order here, a good anchor. Warn students NOT to over-generalise: NORAD number is cataloguing order, not launch order, and the two only loosely track.
  • The ISS designator 1998-067A is worth a spotlight: the "A" piece is Zarya, the first module; dozens of later 1998-067 pieces (visiting vehicles, deployed CubeSats) share the launch root with different piece letters. This is the clearest real example of the piece-letter idea.
  • If a value on OrbitalWiki differs from another source a student finds, treat that as a teachable provenance moment (see the "finding conflicting metadata" lesson), not an error to hide.

Answer key

HST (Hubble), NORAD / COSPAR
20580 / 1990-037B (launch year 1990)
ISS (Zarya), NORAD / COSPAR
25544 / 1998-067A (launch year 1998)
Terra, NORAD / COSPAR
25994 / 1999-068A (launch year 1999)
Aqua, NORAD / COSPAR
27424 / 2002-022A (launch year 2002)
Landsat 8, NORAD / COSPAR
39084 / 2013-008A (launch year 2013)
Sentinel-2A, NORAD / COSPAR
40697 / 2015-028A (launch year 2015)
NOAA 20 (JPSS-1), NORAD / COSPAR
43013 / 2017-073A (launch year 2017)
(a) Lowest NORAD number?
Hubble, 20580, catalogued earliest of the seven, consistent with its 1990 launch.
(b) Do the Earth-observation satellites share a COSPAR root?
No. Terra (1999-068A), Aqua (2002-022A), Landsat 8 (2013-008A), Sentinel-2A (2015-028A) and NOAA 20 (2017-073A) each launched separately in different years, so every one has a distinct COSPAR year and launch number. Similar mission ≠ shared identifier.

How to cite

Cite the specific record pages used, with the access date, e.g. "OrbitalWiki, satellite record 25544 (ISS), retrieved 2026-07-24, https://www.orbitalwiki.com/satellites/25544". Because the catalog updates over time, always include the retrieval date.

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