NOAA Weather Satellites

The US National Oceanic and Atmospheric Administration (NOAA) operate a number of earth observation satellites.  Of interest to us are the NOAA series of low-earth-orbit satellites , which fly in sun-synchronous polar orbits, and which continuously transmit real-time earth imagery within the 137MHz space-downlink band.

Currently there are three NOAA satellites which may be received with modest VHF receiving equipment, namely NOAAs 12, 15 and 17.  These satellites orbit at an altitude of ≈800km above the Earth's surface, with the plane of their orbits approximately aligned with the plane of the Earth's day/night terminator.  In low earth orbit, satellites have a ≈100 minute orbital period, and for a mid-to-low latitude observer, each NOAA satellite will make 2-3 passes, each morning and evening.

The simple analog mode of NOAA image transmission is known as Automatic Picture Transmission (APT), which is broadcast in the 137MHz band.  A higher resolution digital mode known as High Resolution Picture Transmission (HRPT), is transmitted at frequencies ≈1.7GHz.  The current status of the APT and HRPT transmitters aboard the NOAA satellites is broadcast daily.

The latest three NOAA satellites are very similar in design, and were designated NOAAs 'K', 'L' and 'M' at launch, being later renamed to NOAA 15, 16 and 17 respectively.  For technical folk who want to learn fine details of 'KLM' series NOAA satellites, the NOAA KLM User's Guide is an excellent and comprehensive reference.  Of particular interest for 137MHz APT image reception, is Section 4.2 of the Guide.

Sometime during 2005, a new replacement NOAA satellite will be launched from Vandenberg AFB, California.  This one has a newer design than the 'KLM' series, and is named 'NOAA-N'.  Space watchers can keep an eye on on the Spaceflight Now news service Launch Schedule, to check the current NOAA-N launch status.  At present (January, 2005) NOAA-N is scheduled for launch on March 10, 2005.  For interest, one of the new NOAA-N series satellites being assembled in Sunnyvale, California, suffered a mishap during September 2003, in what was rather understatedly termed an "anomaly".  The full story may be read at  These images and story also demonstrate how large and complex these spacecraft are.  A full report into this accident was released by NASA during October, 2004.

During 2004, NOAA/NASA issued an excellent 'booklet' describing the NOAA-N spacecraft.  This comprehensive, well illustrated and eye-catching document, describes in plain language the various instruments aboard the NOAA-N spacecraft, as well as the history of NOAA polar orbiters, the launch, and operational details.  If you are seeking comprehensive but readable description of how NOAA polar orbiting satellites work, this is the document for you.  This booklet may be downloaded as a 40-page 1.4MB pdf file.