Public Release: 

MSX Instruments Observe Small Magellanic Cloud

Johns Hopkins University Applied Physics Laboratory

The Science Team for the Midcourse Space Experiment (MSX) -- a Ballistic Missile Defense Organization satellite launched in April -- has obtained two unique images of the Small Magellanic Cloud (SMC), a small companion galaxy to our own galaxy, the Milky Way. The images represent at least a five-fold improvement in resolution and sensitivity over previous experiments.

These "first light" images were made with the MSX Spatial Infrared Imaging Telescope (SPIRIT III), built by the Space Dynamics Laboratory of Utah State University, and by the MSX Ultraviolet Visible Imagers and Spectrographic Imagers (UVISI), built by The Johns Hopkins University Applied Physics Laboratory (JHU/APL).

Data collection was directed by the MSX Celestial Backgrounds Principal Investigator Team, led by Dr. Stephan D. Price of the U.S. Air Force Phillips Laboratory Geophysics Directorate. MSX Project Scientist is Dr. John D. Mill of the Environmental Research Institute of Michigan. MSX Chief Scientist is Dr. A.T. Stair, Jr., of Visidyne, Inc.

The images cover the same field of 3.5° by 3.5°. They are the first observations at the respective wavelengths to cover the entire galaxy at high sensitivity and good spatial resolution.

The images are available on the World Wide Web from the official MSX homepage at, under the "Program News & Info: Press Releases" section. They are also available on the JHU/APL homepage at, under the "PR" section. Color prints of the images can be obtained from the JHU/APL Public Affairs Office.

Image 1 is a 12 micron (bandpass 8-15 microns) image from the IRAS Sky Survey Atlas, until now the best infrared image of the SMC. The image has a resolution of approximately 4 to 5 arc minutes and contains four bright sources, two of which are in regions of extended emission in the densest part of the galaxy.

Image 2 is the MSX SPIRIT III radiometer Band A (6-11 microns) image of the SMC. The resolution is about 0.3 arc minutes (90 microradians). The extended source in the IRAS image is resolved into a rhomboid-shaped group of sources with no diffuse emission. This demonstrates that the markedly smaller footprint of SPIRIT III easily resolves background sources in a region with a high density of sources.

Image 3 is a visible image of the SMC, which appears as the faint semi-elliptical patch in the center. The image, with a resolution of approximately 0.1 arc minutes, was taken from the Palomar digitized survey of the region observed by MSX. Its fuzzy appearance is due to the high concentration of ordinary stars with similar brightness in the galaxy.

Image 4 is the MSX UVISI image. This is the first time the entire SMC has been imaged in the ultraviolet (from 200 to 300 nm). Since light in this wavelength range is absorbed by atmospheric ozone, images must be made from space. The UVISI instruments are uniquely designed to survey diffuse backgrounds and so have a footprint about 100 times larger than that of the Hubble Space Telescope. Many of the sources seen in the visible image are easily identifiable in the UVISI image. The major difference lies in the prominence given by UVISI to hot gas and stars. Comparisons such as this give astronomers valuable insight into the evolution of galaxies.

The infrared spectral region is ideal for observing cool sources and objects enshrouded in dust. Indeed, the "stars" in the infrared image either are ordinary stars, cool giant stars or stars embedded in circumstellar dust. The ultraviolet, on the other hand, more readily detects very hot stars, stars with surface temperatures in excess of 15,000°K, and nebulae which contain such hot objects.

MSX is the first system demonstration in space of technology to characterize ballistic missile signatures during the "midcourse" flight phase between booster burnout and missile reentry. During its five-year lifetime, MSX will detect, track, and discriminate realistic targets against terrestrial, Earth limb, and celestial backgrounds. The satellite's imaging capabilities will also support a wide variety of "dual-use" research involving global atmospheric change, astronomy, and space contamination and debris.

The observatory-class MSX satellite was launched on April 24, 1996, from Vandenberg Air Force Base, Calif., into a high-inclination, circular, near sun-synchronous Earth orbit at 561 miles (903.5 kilometers) altitude. Round-the-clock operations are being conducted from JHU/APL in Laurel, Md. All MSX sensors have completed on-orbit characterization and are now exceeding planned data return rates.

MSX management for BMDO includes Lt. Col. Bruce D. Guilmain, Program Manager, and Maj. Peter Kurucz, Deputy Program Manager. APL Program Manager is Mr. Max Peterson.

Principal investigators for the MSX mission are assigned according to major program experiment areas. In addition to Dr. Price, they include: Mr. Glenn Light, Early Midcourse; Mr. William T. Prestwood, Cooperative Targets; Dr. E. Michael Gaposchkin, Space Surveillance; Dr. Gerry J. Romick, Shortwave Terrestrial Backgrounds; Dr. O. Manuel Uy, Contamination; Dr. Thomas L. Murdock, Data Certification and Technology Transfer; and Mr. Robert R. O'Neil, Earthlimb/Auroral Backgrounds. The MSX program is supported by approximately 100 scientists from 30 institutions.

For more information, contact the BMDO External Affairs Office at (703) 695-8743, or Luther Young, JHU/APL Public Affairs, at (301) 953-6268 / MSX mission updates can be accessed at

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