NOAA18 has been a favourite of space hobbyists since it's launch in 2005, providing imagery from it's polar orbiting pattern to support meteorological prediction and warning. Transmitting openly on the 137MHz band, it was a go-to satellite for those in the Northern hemisphere interested in getting a live image direct from space on it's pass.
On May 31st, the S-band transmitter, STX4, experienced a power drop from 7W to 0.8W. The only reamining transmitter used for up-link and downlink, this jeaopardized the ability to ensure safe operation of the spacecraft. Based on NOAA's requirement to responsibly manage on-orbit assets, NOAA began the decomissioning of NOAA-18 on June 6th.
The decomissioning phase requires the power-down of equipment and the disconnection of batteries, the pointing of solar arrays away from the sun and depletion of any remaining propellant while parking the satellite in a safer, less-congested orbital path. Due to the nature of the propulsion systems it is not possible to safely bring NOAA-18 down, therefore she will remain in a graveyard orbital pattern for the forseeable future.
NOAA-18 has suffered several failures of equipment over it's lifespan including the reliance on backup gyroscopes, the loss of communications on it's S-band transmitters and degredation/failure of sensors.
The NOAA-15 and NOAA-19 craft are also due to be classified as "end-of-life" on June 16th, but may continue transmitting data for hobbyists to utilise with the caveat no attempts would be made to rectify equipment failures.
Keywords: Space Mission NOAA18 Weather Satellite Decommission NOAA