As the orbit of Comet Hale-Bopp (C/1995 O1) brings it closer to the Sun in late March, NASA and agency-supported scientists will study the large and bright comet using sounding rockets, spacecraft and ground-based observations. Using NASA's Hubble Space Telescope, Hale-Bopp's nucleus was measured at roughly three to four times larger than that of comet Halley (six miles in diameter), making it one of the largest comets ever observed. Researchers are studying Hale-Bopp to better understand comets, primitive bodies of loosely-packed ice and dust that many scientists consider the best-preserved remnants of the early Solar System.

Other agency activities, including a media day for coverage of the sounding rocket launches, and special Internet home pages for posting images obtained by NASA missions as well as amateur astronomers, are outlined below with points of contact and other relevant information.

Sounding Rocket Campaign

The Wallops Flight Facility (WFF), Wallops Island, VA, will conduct four sounding rocket launches starting March 24 through April 5. The missions will be launched for NASA by the U.S. Navy at the White Sands Missile Range (WSMR), NM. The payloads, launched on two-stage Black-Brant IX rockets, will observe the comet in the ultraviolet wavelengths of light for about five minutes before returning to Earth. The payloads will be recovered following a parachute descent at White Sands. Images of the sounding rocket activity at WSMR will be posted to the Internet at:

WFF and WSMR will host a media day at White Sands Missile Range from noon to 4 p.m. MST, March 24. Dr. Alan Hale, co- discoverer of the comet, will be at the site to speak to reporters. Media also are invited to cover the 8:15 p.m. MST launch. For clearance to visit White Sands, call the White Sands Public Affairs Office (PAO) at 505/678-1134. For more information on the sounding rocket campaign, call WFF PAO at 757/824-1579.

Ulysses spacecraft

The joint NASA/European Space Agency Ulysses spacecraft, now in solar orbit, will study what happens to comets as they are exposed to different solar wind conditions at various solar latitudes. Hale-Bopp is about to enter the Sun's lower latitude zone, where solar wind (a continuous outflow of charged particles streaming from the Sun in all directions at a million miles per hour) is disturbed compared with the equatorial regions. Dramatic changes in the comet's plasma tail are expected to occur at these lower celestial latitudes.

A related observing program, called "Ulysses Comet Watch," a collaboration between the Jet Propulsion Laboratory (JPL), Pasadena, CA, and the University of Colorado, will provide images from more than 200 amateur observers around the world. These images will be posted on the Ulysses Comet Watch home page on the Internet at Observations will continue to be posted after the comet makes its closest approach to the Sun on April 1.

Hubble Space Telescope

NASA's Hubble Space Telescope has made a series of observations of the comet, particularly the nucleus, since September 1995. Hubble cannot observe Hale-Bopp during the next few months because the comet is too close to the Sun -- Hubble's sensitive detectors could be damaged if pointed in that direction. The last observation was made on Oct. 18, 1996, and the next possible opportunity will be this autumn.

Dr. Harold Weaver will publish the results of his observations with Hubble in the March 28 issue of Science magazine. For more information, contact the Space Telescope Science Institute (STScI), Baltimore, MD, at 410/338-4514. Images already obtained by Hubble are available from the Internet at

Other NASA Comet Investigations

NASA's Polar spacecraft will make observations of Hale-Bopp using ultraviolet and visible imaging instruments. For more information call the Goddard Space Flight Center, PAO, Greenbelt, MD, at 301/286-0697. Images obtained by Polar will be posted to the Internet site at: :

Scientists have been using NASA's Infrared Telescope Facility, Mauna Kea, HI, to observe Hale-Bopp in the infrared region of the spectrum. Their observations will be made through Hale-Bopp's perihelion and continue until summer. For more information call NASA Headquarters at 202/358-1547.

NASA also will fly a mid-deck experiment on the Space Shuttle Discovery's STS-85 mission in July. The experiment is the Southwest Ultraviolet Imaging System, designed to complement the capabilities of the 5-10 minute sounding rocket flights by observing the comet more extensively during the Shuttle's 11-day mission. For more information call NASA Headquarters at 202/358-1547.

In addition, NASA and the National Science Foundation are collaborating on ground-based observations and analyses of Hale- Bopp. For information, contact NASA Headquarters at 202/358-1547.

JPL "Comet Chasers: On the Trail of a Comet" Public Event

JPL will host a public event called "Comet Chasers: On the Trail of a Comet" on Friday, April 11, at JPL. The event is co- sponsored by the Galileo and Stardust projects. Galileo, which is touring the Jovian system, observed the 1994 Comet Shoemaker-Levy 9 impact on Jupiter. Stardust will launch in 1999, capture samples of comet dust from the Comet Wild-2 and return them to Earth for study. Activities will include a comet viewing session (weather permitting), and a round-table discussion of the study of comets and NASA's role in comet studies, featuring David Levy, co- discoverer of Comet Shoemaker-Levy 9, Dr. Don Yeomans of JPL, and Dr. Alan Hale and Thomas Bopp, co-discoverers of Comet Hale-Bopp. The panelists also will discuss NASA's Stardust mission to Comet Wild-2 in 2004. For more information, call 818/354-5011.

Web Sites, Images, Information and Experts

In addition to the Internet sites already listed, the JPL Hale-Bopp Home Page is a comprehensive information and image resource, including many images taken by amateur observers. The address is:

Other images and information and links will be posted at the Today@NASA home page: Amateur astronomers who have images of Hale-Bopp in electronic file format are invited to post their pictures to a NASA web page at URL: Prior to posting, one must first register following the prompts on that page.

Comet researchers are available for interviews, both in person and via satellite, at NASA Headquarters as well as GSFC, WFF, JPL and STScI and other Centers. Contact the respective Public Affairs Offices for further information.

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