January 17, 1998

NEAR spacecraft to shine brightly Thursday night

On Thursday night-Friday morning, January 22-23, the Near Earth Asteroid Rendezvous (NEAR) spacecraft will swing by the Earth primarily to change its orbital plane to match that of the asteroid 433 Eros, NEAR's target for an early 1999 rendezvous. As NEAR approaches the Earth, its almost 100 square feet of solar panels will be rotated to reflect sunlight to several regions of the U.S.A., providing a unique opportunity to see with the naked eye an interplanetary spacecraft flying through space. Although NEAR will be about 9000 miles over the North Pacific Ocean at the time, it is expected to briefly shine as bright as Capella, among the brightest stars in the sky. These NEAR sunglints will be visible from 1:25 am to 1:49 am EST January 23rd (10:25 pm to 10:49 pm PST January 22nd), about an hour before NEAR's closest approach to the Earth over 300 miles above the Middle East. More about NEAR's Earth swingby is available in a press release from the Johns Hopkins University's Applied Physics Laboratory (APL). This site lists the following times to see the sunglint:

Areas Most Likely to See NEAR's Sunglint:

Region                 (Friday Jan. 23) Sunglint Time

s. New England, e. New York*              1:25 am EST
Midwest (s. Ontario, Detroit area)        1:26 am EST
Midwest (Chicago & Kans. City areas)     12:26 am CST
s. Nebr., n. Missouri, central Illinois  12:28 am CST
s. Indiana, Cincinnati, W. Va.            1:28 am EST
e. Virginia, DC area, Md., s. Penn.*      1:29 am EST
Central Va., central N. Car., S. Car.     1:30 am EST
Georgia, central & e. Tenn.*              1:31 am EST
Georgia (again), Florida peninsula        1:32 am EST
Florida peninsula (again)*                1:33 am EST
Louisiana*                               12:35 am CST
eastern Texas*                           12:37 am CST
San Angelo to Midland-Odessa, Texas      12:39 am CST

Region               (Thursday Jan. 22) Sunglint Time

Colorado*                                11:27 pm MST
s. New Mexico, s. Arizona                11:39 pm MST
southern California*                     10:40 pm PST
southern Nevada                          10:41 pm PST
Utah*                                    11:41 pm MST
central Calif. (Fresno area)             10:43 pm PST
n. Calif. (San Francisco-Sacramento)*    10:44 pm PST
Oregon                                   10:45 pm PST
w. Washington state, s.w. Brit. Col.*    10:46 pm PST
Oahu and Maui, Hawaii*                    8:48 pm HST

*These are "targeted" regions that will see the flash for about 
half a minute. Other areas will see the flash for only a few seconds. 
Watch for about three minutes, starting a minute before the listed 

The press release also describes approximately how to find NEAR:

If you are in one of the sunglint regions listed above, look for the brightest star above the northwestern horizon, Capella, which will be about halfway between the horizon and straight overhead for the East Coast, and higher on the West Coast. Hold your hand at arm's length and stretch out your fingers, putting the end of your little finger at the top at Capella. The tip of your thumb, pointing straight down from Capella, will mark the approximate location where the sunglint will occur in the constellation Perseus, about 20 degrees below Capella. The glint should be very noticeable, about as bright as Capella. The press release Web site includes a figure illustrating this.

Hawaii will see the brightest flash, as bright as Sirius, the brightest star in the night sky. The view there will differ from other parts of the U.S., with Capella being above the northern horizon and the glint being below and to the left of Capella.

Sky charts for locating the glint areas with binoculars and a map showing the path of the glint zone (100 to 200 miles wide, depending on the geometry) will soon be on IOTA's Web sites at http:/www.sky.net/~robinson/iotandx.htm and http://www.anomalies.com/iota/splash.htm. The U.S.A. map showing the path has no times; use the table above for the time for your location. A version of the map with Universal Times will be posted on the IOTA sites either late tonight or tomorrow. A local-time version will be posted either tomorrow or Monday, with the best-quality version being posted Monday at the NEAR Web site. Two sky charts are posted, one calculated for the Washington-Baltimore area but which can be used for the eastern half of the U.S.A., and one for Los Angeles that will be good enough for the western half of the country. Similar charts for about a dozen other locations will be posted Monday or Tuesday probably at the NEAR site but possibly at the IOTA sites. Anyone needing a preliminary version of one of these charts for other regions for publication can contact me to obtain it by fax.

An animation showing the path of the sunglint can be found on the NEAR Web site: http://sd-www.jhuapl.edu/NEAR/.

That site also includes a chart of Perseus showing in more detail where the sunglint will appear for different cities, suitable for those who want to find the sunglint location with powerful binoculars or telescopes. That site indicates that it might be best to see the sunglint with a telescope, but that is misleading; it will be easy to see with the naked eye.

NEAR's pointing should be accurate to better than 0.1 deg., less than a fifth of the diameter of the Sun. But the solar panels could be misaligned with the spacecraft axis by a few tenths of a degree, and (unlikely) even as much as a degree. So observers at least half a pathwidth (and maybe more) outside of the predicted path have a chance to see at least part of the sunglint. It may occur in steps since NEAR has 4 solar panel arrays, each of which might be misaligned a little relative to each other.

Timed observations of the sunglint are sought to try to measure the solar panel alignments precisely. Such observations could be made with a camcorder (use manual focus), or visually with a tape recorder, like timing a grazing or asteroidal occultation. Record WWV shortwave time signals along with the event for timing. More about recording and reporting the sunglint will be distributed later and posted on the IOTA Web sites.

David Dunham, IOTA and NEAR Mission Design
Telephones: 301-474-4722 at home and 301-953-5609 at APL
E-mail: dunham@erols.com at home and David.Dunham@jhuapl.edu at APL

John Hopkins Univerity Applied Physics Laboratory Press Release

15 January 1998


NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft, built by The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., will become the first interplanetary spacecraft to be seen with the naked eye when it swings by Earth Jan. 22-23. The spacecraft's solar panels will reflect the sun's rays onto the Earth in a greeting as it flies by for an adjustment of its trajectory to correctly align the spacecraft for a rendezvous with asteroid 433 Eros, its mission target.

Launched Feb. 17, 1996, NEAR completed a flyby of the asteroid Mathilde in June 1997 and is now on its way back to Earth. Late Thursday, Jan. 22, the spacecraft approaches Earth over the Pacific Ocean traveling at about 20,000 mph. Because the United States will be in darkness as NEAR approaches, if there is no cloud cover, several geographic areas will be able to see the sun reflecting off the spacecraft's solar panels, which will act as large mirrors. These sunglints will be visible on the East Coast, Friday, Jan. 23, at about 1:30 a.m. EST and the West Coast at about 1:45 a.m. EST (Thursday, 10:45 p.m. PST). (See below for more details.)

The spacecraft then swings around the Aleutian Islands and over Siberia before reaching its closest point to Earth, about 336 miles above Ahvaz in southwest Iran, Friday, Jan. 23, at 11:23 a.m., local time (2:23 a.m. EST), traveling at about 29,000 mph-its fastest speed for the swingby. Although NEAR will be close to Earth at this time, daylight may obscure its image. The spacecraft then swings over Africa and on to Antarctica before pulling away from the Earth at a speed of about 15,000 mph. The swingby will have changed NEAR's trajectory to approximately 11 degrees south of the Earth's ecliptic plane, the orbital path the Earth takes as it circles the sun, and put the spacecraft on target for its Jan. 10, 1999, rendezvous with Eros.

NEAR scientists and engineers are using the swingby as an opportunity to test performance and calibration of the spacecraft's six instruments and to practice coordinated multi-instrument observations of the type that will be used at Eros. The spacecraft's Laser Rangefinder will be used to conduct a two-way laser link with the Goddard Geophysical and Astrophysical Observatory, operated by the NASA Goddard Space Flight Center in Greenbelt, Md. Weather permitting, the laser test will take place between Jan. 15-19. If successful, this will be the first-ever two-way (ground to space and back again) laser link to an interplanetary spacecraft.

The Multispectral Imager, a visible light camera that will help determine the physical characteristics of Eros, and the NEAR-Infrared Spectrograph, used to study surface minerals, will be calibrated by comparing their readings of geological features with proven measurements of the same areas. These instruments will also be used to take images of the Earth along the spacecraft's path. The images will be combined to produce a movie from a series of images taken over Asia, Africa, and Antarctica, which will be released several weeks after the swingby. NEAR's Magnetometer will be calibrated by comparing swingby data with known measurements of the Earth's magnetic field.

Other activities during the swingby will include using the X-Ray/Gamma-Ray Spectrometer to observe celestial gamma ray bursts and to collect data on gamma ray and x-ray backgrounds. These data are needed so scientists can better remove background impurities from the measurements to be made at Eros.

NEAR is expected to capture its first images of Eros, a 25-mile-long near-Earth asteroid, a few months prior to the 100th anniversary of the asteroid's discovery on Aug. 13, 1898. After reaching Eros a year from now the spacecraft will start its orbit about 600 miles above the asteroid's surface, descending to 200 miles by February and coming as close as 10 miles during its yearlong study. Scientists will thoroughly map Eros and will examine its surface composition and physical properties. On Feb. 6, 2000, the mission is expected to end with a controlled descent onto the asteroid, sending dozens of high-resolution pictures as it closes in on Eros.

The NEAR mission will be the first close-up study of an asteroid. APL, the first non-NASA center to conduct a NASA planetary mission, is managing the mission for NASA's Office of Space Science.

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