NOAA-18, known before launch as NOAA-N, is a weather forecasting satellite run by NOAA. NOAA-N (18) was launched on May 20, 2005, into a sun-synchronous orbit at an altitude of 854 km above the Earth, with an orbital period of 102 minutes. It hosts the AMSU-A, MHS, AVHRR, Space Environment Monitor SEM/2 instrument and High Resolution Infrared Radiation Sounder (HIRS) instruments, as well as the SBUV/2 ozone-monitoring instrument. It is the first NOAA POES satellite to use MHS in place of AMSU-B.
APT transmission frequency is 137.9125 MHz (NOAA-18 changed frequencies with NOAA-19 on June 23, 2009).
AMSU-A (Advanced Microwave Sounding Unit - A)
AVHRR/3 (Advanced Very High Resolution Radiometer / 3)
HIRS/4 (High-resolution Infra Red Sounder / 4)
MHS (Microwave Humidity Sounding)
S&RSAT (Search & Rescue Satellite-Aided Tracking System)
SBUV/2 (Solar Backscatter Ultraviolet / 2)
DCS/2 (Data Collection System / 2)
SEM/MEPED (SEM / Medium energy proton detector)
SEM/TED (SEM/ Total Energy Detector)