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)

Sun synchronous
102 minutes
Meteorology, agriculture and forestry, environmental monitoring, climatology, physical oceanography, volcanic eruption monitoring, ice and snow cover, total ozone studies, space environment, solar flux analysis, search and rescue