The Stratospheric Aerosol and Gas Experiment (SAGE I - III) role in the EOS program is to provide global, long-term measurements of key components of the Earth's atmosphere. The most important of these are the vertical distribution of aerosols and ozone from the upper troposphere through the stratosphere. In addition, SAGE III also provides unique measurements of temperature in the stratosphere and mesosphere and profiles of trace gases such as water vapor and nitrogen dioxide that play significant roles in atmospheric radiative and chemical processes. The SAGE III Science Team functions in a dual role where they ensure the data quality and interpret the SAGE III data in the broader context of global change.

SAGE I was launched onboard AEM-2 (Applications Explorer Mission 2) in 1979, SAGE II aboard ERBS (Earth Radiation Budget Satellite) in 1984, and SAGE III onboard a Russian Meteor-3M satellite on Dec. 10, 2001.

Objectives

The primary scientific objective of the three SAGE missions is to obtain high quality, global measurements of key components of atmospheric composition and their long-term variability.These measurements are vital inputs to the global scientific community for improved understanding of climate, climate change, and human-induced ozone trends.

Instrument

The Stratospheric Aerosol and Gas Experiment I (SAGE I) instrument was a sun photometer that measured the attenuation of solar radiation through the Earth's atmosphere during spacecraft sunrise and sunset in four spectral regions centered at wavelengths of 1000, 600, 450, and 385 nanometers for nearly global measurement of aerosol extinction profiles and ozone and nitrogen dioxide concentration profiles. SAGE I was launche in February 1979 abord the Applications Explorer Mission-B (AEM-B) satellite. The AEM-B satellite was placed in an orbit of approximately 600 kilometers at an inclination of 56 degrees to extend the latitudinal coverage for the solar occultation measurements from 79 degrees South to 79 degrees North. The (SAGE I) instrument collected data for almost three years until the (AEM-B) satellite power subsystem failed in November, 1981.

The SAGE II instrument is a seven-channel Sun photometer using a Cassegrainian-configured telescope, holographic grating, and seven silicon photodiodes, some with interference filters, to define the seven spectral channel bandpasses, which are centered at 1020, 940, 600, 525, 453, 448, and 385 nanometer The SAGE II sensor was launched into a 57-degree inclination orbit aboard the Earth Radiation Budget Satellite (ERBS) in October 5, 1984 and decomissioned in August 2005.

SAGE III is a natural and improved extension of the SAGE II experiments. The spectrometer measures solar radiation from 280 nm to 1040 n, and 1-2 nm resolution. An additional photo detector measures radiation at 1550 nm. . Additional aerosol information is provided by a discrete photodiode at 1550 nm. This configuration enables SAGE III to make multiple measurements of absorption features of target gaseous species and multi-wavelength measurements of broadband extinction by aerosols. The first SAGE III instrument was launched aboard Meteor 3M-1 in December 2001

SAGE III measurements:

• Aerosol Extinction
• Water Vapor (H2O) Concentration
• Nitrogen Dioxide (NO2) Concentration and Slant Path Column Amount
• Nitrogen Trioxide (NO3) Concentration (lunar)
• Ozone (O3) Concentration and Slant Path Column Amount
• Chlorine Dioxode (OClO) Concentration (lunar)
• Pressure Profile
• Temperature Profile (solar)
• Cloud Presence

Data Access

General Data Product Level Definition

Data of all three instruments can be accessed on the ATMOSPHERIC SCIENCE DATA CENTER site.

A new version of the IDL reader software is available and is needed to accurately access Version 3 products. Previous versions may not generate obvious software failures, but could lead to misleading results. The latest versions of the SAGE III sponsored software tools and data user's guide can be obtained from the SAGE III website.

SAGE III Data User's Guide

Links

• SAGE I
• SAGE II
• SAGE III

Contact

If you would like to know more about the SAGE instrument or the SAGE data products contact wdc@dlr.de.