NOAA-15

NOAA-15 is a polar-orbiting operational environmental satellite (POES) operated by the United States National Oceanic and Atmospheric Administration (NOAA). Launched on May 13, 1998, it was the first in the Advanced TIROS-N (ATN) series of satellites designed to provide global meteorological and environmental data. Its primary mission is to collect data for weather forecasting, climate monitoring, and environmental studies, as well as to support search and rescue operations.

Mission Overview

NOAA-15 was launched from Vandenberg Air Force Base aboard a Titan II rocket. It was designed for a two-year operational life but has significantly exceeded this, continuing to provide valuable data for over two decades. As part of the POES constellation, it operates in a sun-synchronous orbit, allowing it to observe the entire Earth's surface twice daily, providing consistent lighting conditions for data collection. The satellite plays a crucial role in providing essential data for numerical weather prediction models and for monitoring various environmental phenomena.

Instruments

NOAA-15 carries a suite of instruments designed to collect a wide range of atmospheric and surface data:

• Advanced Very High Resolution Radiometer (AVHRR/3): This instrument measures visible and infrared radiation, providing data for cloud analysis, sea surface temperature, vegetation index, and ice detection.
• TIROS Operational Vertical Sounder (TOVS) Suite: Comprising three instruments, TOVS provides atmospheric temperature and moisture profiles:
  • High-resolution Infrared Radiation Sounder (HIRS/3): Measures infrared radiation at 20 spectral channels to determine atmospheric temperature and moisture profiles.
  • Advanced Microwave Sounding Unit-A (AMSU-A): A 15-channel microwave radiometer that measures temperature profiles from the Earth's surface to the upper atmosphere, particularly useful in cloudy conditions where infrared instruments are less effective.
  • Advanced Microwave Sounding Unit-B (AMSU-B): A 5-channel microwave radiometer that measures moisture profiles in the atmosphere.
• Space Environment Monitor (SEM/2): Measures the flux of charged particles in the Earth's magnetosphere, providing information on solar activity and space weather.
• Argos Data Collection System (DCS/2): Collects and relays data from environmental platforms, such as buoys, remote weather stations, and wildlife tracking tags, to ground stations.
• Search and Rescue Satellite-Aided Tracking (SARSAT) System (SARR): Detects distress signals from emergency beacons on aircraft, vessels, and from individuals, relaying them to ground stations for coordination of search and rescue efforts.

Orbit

NOAA-15 maintains a near-circular, sun-synchronous, low Earth orbit at an altitude of approximately 833 kilometers (518 miles). Its orbital inclination is around 98.7 degrees, ensuring it crosses the equator at roughly the same local solar time on each pass, which is critical for consistent long-term data collection. The sun-synchronous nature of the orbit allows for uniform illumination conditions over observed regions, aiding in the interpretation of visual and infrared data.

Significance and Status

NOAA-15 was a foundational satellite in the POES program, being the first to carry the full complement of AMSU-A and AMSU-B instruments, which significantly enhanced its capability for atmospheric sounding, especially in cloudy conditions. Despite being well past its designed operational life, NOAA-15 continues to provide valuable, though sometimes degraded, data, contributing to the global observing system. Its longevity underscores the robust design of the ATN series and its continued utility as a component of the international network for meteorological and environmental monitoring.