Since the 1960s, NASA has developed polar-orbiting operational environmental satellites (POES) for the National Oceanic and Atmospheric Administration (NOAA). NOAA-M, the latest NOAA spacecraft, is scheduled for launch in the summer of 2002.

Illustration of NOAA-M in orbit. Photo: NASA

The NOAA satellites carry instruments that observe our Earth and provide global data for NOAA's operational user requirements including short-, medium-, and long-range weather forecasts. The operational system consists of two polar-orbiting satellites. One operates in an afternoon orbit and the other in a morning orbit with equator crossing times chosen to maximize the usefulness of the data for a variety of applications.

These spacecraft monitor the entire Earth, providing atmospheric measurements of temperature, humidity, ozone and cloud images as they track weather patterns that affect the global weather and climate. The satellites send millions of global measurements daily to NOAA's Command and Data Acquisition stations in Fairbanks, Alaska, and Wallops Island, Virginia, and to its data processing center in Suitland, Maryland, adding valuable information to forecasting models, especially for ocean areas, where conventional groundbased data are lacking.

Currently, NOAA has two operational polar orbiters: NOAA-16, launched in September 2000, into a 2:00 p.m. local solar time orbit and NOAA-15, launched in May 1998, into a 7:30 a.m. local solar time orbit. NOAA-M will replace NOAA-15 in a 10:00 a.m. local solar time orbit. The new 10:00 a.m. orbit will allow NOAA-M to carry the same instruments as the 2:00 p.m. satellite (both cross the equator two hours away from noon), and allows for the generation of the same product suite from each orbit.

NOAA-M will be renamed NOAA-17 after achieving orbit. The satellites receive a letter designation while under construction on the ground and are then renamed with a numerical designation after launch. This is done because the satellites are built in alphabetical order but are not necessarily launched in this same order. Therefore, to avoid confusion, they are numbered upon reaching orbit.

NASA and NOAA are actively engaged in a cooperative program to develop and launch the NOAA Polar Operational Environmental Satellites (POES). NOAA is responsible for program requirements, funding and the on-orbit operation of the multisatellite system. NOAA also determines the need for satellite replacement. NOAA designs and develops the ground system needed to acquire, process and disseminate the satellite data. NASA's Goddard Space Flight Center in Greenbelt, Maryland, is responsible for the construction, integration and verification testing of the spacecraft, instruments and unique ground equipment.

NOAA-M will be launched by the U.S. Air Force on a refurbished ballistic missile, a Titan 2. After launch, NASA checks out the satellite to assure it meets its performance requirements. NASA turns operational control of the spacecraft over to NOAA after 21 days of comprehensive subsystem checkout. An on-orbit instrument performance verification period lasts an additional 24 days.

Illustration of NOAA-M's orbit around Earth. Photo: NASA/NOAA

NOAA-M, the latest in the spacecraft series, will broadcast data directly to thousands of users around the world. The spacecraft will continue providing a polar orbiting platform to support the environmental monitoring instruments for imaging and measuring the Earth's complex coupled systems -- it's atmosphere, its surface and cloud cover. Observations include information about Earth radiation, sea and land surface temperature, atmospheric vertical temperature, water vapor and ozone profiles in the troposphere and stratosphere.

Measurement of proton and electron flux at orbit altitude, remote platform data collection and the Search and Rescue Satellite-aided Tracking system (SARSAT) are also supported. NOAA-M will be the third in the series to support a new suite of dedicated microwave instruments to generate improved temperature and moisture profiles and surface and hydrological products in cloudy regions where visible and infrared instruments have decreased capability.

The NOAA satellite series is designed for a two year mission life, but historically, they have averaged a lifetime almost twice as long. The satellite has a three axis body stabilized design. This enables the satellite to point accurately toward the Earth and provide continuous global images of cloud cover; surface parameters such as snow, ice and vegetation; and atmospheric temperatures, moisture and aerosol distributions. The satellite is also able to collect and relay information from fixed and moving data platforms, such as buoys, freefloating balloons and remote weather stations.

Each satellite consists of an imaging system, the Advanced Very High Resolution Radiometer and a sounding suite of instruments consisting of the High Resolution Infrared Radiation Sounder and the Advanced Microwave Sounding Units, one for temperature profiles and one for moisture profiles.

NOAA-M facts
Main body	13.75 feet long 6.2 feet diameter
Solar Array	8.96 by 20.16 feet
Weight at liftoff	4,920 pounds
Orbit	470 nautical miles, inclined 98.6 deg.
Design life	At least 2 years
Satellite Cost	$202 million
Source: NASA press kit

The NOAA satellites also include a Space Environment Monitor that provides measurements to determine the intensity of the Earth's radiation belts and the flux of charged particles at the satellite altitude. The monitor warns of solar wind occurrences that may impair long-range communication or high-altitude operations, damage satellite circuits and solar panels, or change drag and magnetic torque on satellites.

Also flying on NOAA-M is the Solar Backscatter Ultraviolet Radiometer. Both an imager and a sounder, the Radiometer produces total ozone maps and measures the ozone distribution in the atmosphere as a function of altitude. In the past, the Radiometer has not flown in the morning POES satellite, but the new 10:00 a.m. orbit permits the collection of ozone data.

A very important mission of these spacecraft is that of lifesaving. Each polar-orbiting NOAA satellite, except NOAA-12, is equipped with a SARSAT system, which receives emergency beacons from ships and aircraft in distress. SARSAT is part of an international satellite system for search and rescue that includes the NOAA spacecraft and the Russian-provided satellite COSPAS. The system consists of the satellites in polar orbit and an international network of Earth stations, which provide global distress alert and location information to appropriate rescue authorities for maritime, aviation and land users in distress. SARSAT has been attributed to saving more than 12,000 lives since it became operational in November 1982.