National Aeronautics and Space Administration

FOR CENTURIES, astronomers gazed from afar at the planets, moons, comets, and asteroids and could only speculate about their physical nature. Looking through telescope eyepieces, anyone could see that other planets had atmospheres. But atmospheres made of what? How hot and dense were they? How fast did their winds blow? And how did the atmospheres change over the seasons?

Astronomers eventually found a way to study planetary atmospheres from Earth: spectroscopy. Light is collected by a telescope and split into its component wavelengths, or spectrum, much as a toy prism spreads sunlight into a rainbow. Patterns in the spectrum reveal detailed information about the temperature, composition, and motions of atmospheres millions to billions of miles away.

Infrared Heterodyne Spectroscopy at Goddard

A team of scientists at NASA's Goddard Space Flight Center in Greenbelt, MD, probes planetary atmospheres using a technique called infrared heterodyne spectroscopy (IRHS). This technique is at the heart of a device called the NASA/Goddard Heterodyne Instrument for Planetary Wind and Composition, or HIPWAC.

The powerful HIPWAC instrument operates at observatories such as the NASA Infrared Telescope Facility and the National Astronomical Observatory of Japan Subaru Telescope on the summit of Mauna Kea, Hawaii. HIPWAC has made valuable observations of a variety of solar system bodies, including Mars, Jupiter, Saturn, Titan, Neptune, and Venus.

This web site explains the IRHS technique, the HIPWAC instrument, and what they are revealing about the solar system. It also provides information for researchers interested in pursuing collaborative research with the NASA/Goddard HIPWAC team.

Observatories operating at the summit of Mauna Kea include, pictured here from left to right, the Subaru Telescope, the twin Keck telescopes, and the NASA Infrared Telescope Facility. HIPWAC has operated at both the Subaru and IRTF facilities. Credit: Kelly E. Fast