A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » News
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

MESSENGER Gains Critical Gavity Assist for Mercury Orbit



 
 
Thread Tools Display Modes
  #1  
Old September 30th 09, 09:43 PM posted to sci.space.news
ron
external usenet poster
 
Posts: 269
Default MESSENGER Gains Critical Gavity Assist for Mercury Orbit

Johns Hopkins University Applied Physics Laboratory
Office of Communications and Public Affairs
Laurel, Maryland
Media Contact: Paulette Campbell
(240) 228-6792

September 30, 2009

FOR IMMEDIATE RELEASE

Note: MESSENGER flyby images available at
http://messenger.jhuapl.edu/index.php

MESSENGER GAINS CRITICAL GRAVITY ASSIST FOR MERCURY ORBIT

MESSENGER successfully flew by Mercury on Tuesday, Sept. 29, gaining
a critical gravity assist that will enable it to enter orbit about
Mercury in 2011 and capturing images of 5 percent of the planet never
before seen. With more than 90 percent of the planet's surface
already imaged, MESSENGER's science team had drafted an ambitious
observation campaign designed to tease out additional details from
features uncovered during the first two flybys. But an unexpected
signal loss prior to closest approach hampered those plans.

At approximately 5:55 p.m. EDT, the spacecraft passed by Mercury at
an altitude of 142 miles and at a relative velocity of more than
12,000 miles per hour according to Doppler residual measurements
logged just prior to the closet approach point. As the spacecraft
approached the planet, MESSENGER's Wide Angle Camera captured a
striking view

http://messenger.jhuapl.edu/gallery/...2&image_id=331

which shows portions of Mercury's surface that had remained unseen by
spacecraft even after the three flybys by Mariner 10 in 1974 and 1975
and MESSENGER's two earlier flybys in 2008.

"This third and final flyby was MESSENGER's last opportunity to use
the gravity of Mercury to meet the demands of the cruise trajectory
without using the probe's limited supply of on-board propellant,"
says MESSENGER mission systems engineer Eric Finnegan of the Johns
Hopkins University Applied Physics Laboratory in Laurel, Md.

A portion of the complicated encounter was executed in eclipse, when
the spacecraft is in Mercury's shadow and the spacecraft -- absent
solar power -- was to operate on its internal batteries for 18
minutes. Ten minutes after entering eclipse and four minutes prior to
the closet approach point, the carrier signal from the spacecraft was
lost, earlier than expected.

According to Finnegan, the spacecraft autonomously transitioned to a
safe operating mode, which pauses the execution of the command load
and "safes the instruments," while maintaining knowledge of its
operational state and preserving all data on the solid-state recorder.

"We believe this mode transition was initiated by the on-board fault
management system due to an unexpected configuration of the power
system during eclipse," Finnegan says. MESSENGER was returned to
operational mode at 12:30 a.m. with all systems reporting nominal
operations. All on-board stored data were returned to the ground by
early morning and are being analyzed to confirm the full sequence of
events.

"Although the events did not transpire as planned, the primary
purpose of the flyby, the gravity assist, appears to be completely
successful," Finnegan adds. "Furthermore, all approach observing
sequences have been captured, filling in additional area of
previously unexplored terrain and further exploring the exosphere of
Mercury."

"MESSENGER's mission operations and engineering teams deserve high
commendation for their professional and efficient approach to last
night's spacecraft safe-mode transition," says MESSENGER principal
investigator Sean Solomon of the Carnegie Institution of Washington.
"They quickly diagnosed the initial problem, restored the spacecraft
to its normal operating mode, and developed plans to recover as much
of our post-encounter science observations as possible. Most
importantly, we are on course to Mercury orbit insertion less than 18
months from now, so we know that we will be returning to Mercury and
will be able to observe the innermost planet in exquisite detail."

Additional information and features from this encounter will be
available online at http://messenger.jhuapl.edu/mer_flyby3.html. Be
sure to check back frequently to see the latest released images and
science results.

###

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and
Ranging) is a NASA-sponsored scientific investigation of the planet
Mercury and the first space mission designed to orbit the planet
closest to the Sun. The MESSENGER spacecraft launched on August 3,
2004, and after flybys of Earth, Venus, and Mercury will start a
yearlong study of its target planet in March 2011. Dr. Sean C.
Solomon, of the Carnegie Institution of Washington, leads the mission
as Principal Investigator. The Johns Hopkins University Applied
Physics Laboratory built and operates the MESSENGER spacecraft and
manages this Discovery-class mission for NASA.

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
MESSENGER is at Mercury Pat Flannery History 69 January 18th 08 01:15 PM
MESSENGER is at Mercury OM[_6_] Policy 4 January 18th 08 01:15 PM


All times are GMT +1. The time now is 01:41 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.