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Earth Swingby Puts NEAR Spacecraft On Final Approach To Eros
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- Subject: Earth Swingby Puts NEAR Spacecraft On Final Approach To Eros
- From: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
- Date: Sat, 17 Jan 1998 22:02:15 GMT
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John Hopkins Univerity Applied Physics Laboratory Press Release
15 January 1998
FOR IMMEDIATE RELEASE
EARTH SWINGBY PUTS NEAR SPACECRAFT ON FINAL APPROACH TO EROS
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.
---------------------------------------------------------
Areas Most Likely to See NEAR's Sunglint:
Region - (Friday Sunglint Sunglint
Jan. 23) Time [Image] Region - (Thursday Jan. 22) Time
s. New England, 1:25 am 11:27 pm
e. New York* EST [Image] Colorado* MST
Midwest (s.
Ontario, Detroit 1:26 am [Image] s. New Mexico, s. Arizona 11:39 pm
area) EST MST
Midwest (Chicago
& Kans. City 12:26 am [Image] southern California* 10:40 pm
areas) CST PST
s. Nebr., n.
Missouri, central 12:28 am [Image] southern Nevada 10:41 pm
Illinois CST PST
s. Indiana,
Cincinnati, W. 1:28 am [Image] Utah* 11:41 pm
Va. EST MST
e. Virginia, DC
area, Md., s. 1:29 am [Image] central Calif. (Fresno 10:43 pm
Penn.* EST area) PST
Central Va.,
central N. Car., 1:30 am [Image] n. Calif. (San 10:44 pm
S. Car. EST Francisco-Sacramento)* PST
Georgia, central 1:31 am 10:45 pm
& e. Tenn.* EST [Image] Oregon PST
Georgia (again), 1:32 am w. Washington state, s.w. 10:46 pm
Florida peninsula EST [Image] Brit. Col.* PST
Florida peninsula 1:33 am 8:48 pm
(again)* EST [Image] Oahu and Maui, Hawaii* HST
Louisiana* 12:35 am
CST
eastern Texas* 12:37 am
CST
San Angelo to 12:39 am
Lubbock, Texas CST
*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 time.
How To Find NEAR as it Swings Past Earth:
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, and will last several
seconds.
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 and
animation showing the path of the
sunglint can be found on the NEAR Web
site: http://sd-www.jhuapl.edu/NEAR/
---------------------------------------------------------
For more information contact Helen Worth, JHU/APL Office of Public Affairs.
Phone: (301) 953-5113; e-mail: Helen.Worth@jhuapl.edu; or fax: (301)
953-6123, or visit the APL NEAR Web page: http://sd-www.jhuapl.edu/NEAR/
B-roll animation of NEAR's Earth swingby and animation photos are available.
See Web page for images.