Image: Messenger and Venus
A computer-generated animation shows the Messenger probe against the backdrop of Venus' disk during this week's flyby.
updated 6/5/2007 10:47:08 PM ET 2007-06-06T02:47:08

The flyby of a NASA spacecraft over Venus could provide new insights about the cloud-shrouded planet, serving as a dress rehearsal for its first rendezvous next year with its main target, Mercury.

On Tuesday, Messenger flew over Venus in a maneuver designed to use the pull of the planet's gravity to slow it down enough that it can slip into the orbit of Mercury. During the flyby, Messenger was to decelerate from 22.7 to 17.3 miles per second (36.5 to 27.8 km/s).

"This change in Messenger's velocity is the largest of the mission," said Messenger mission systems engineer Eric Finnegan, of the Applied Physics Laboratory at John Hopkins University.

Messenger was to approach Venus on the planet's dayside at more than 30,000 miles per hour (48,000 km/h), pass over the boundary separating day from night, and pass within 200 miles (320 kilometers) of the planet's surface while on its night side.

Second pass, with a first for science
The flyby was Messenger's second pass by Venus. During the first flyby, in October 2006, no scientific observations were made because the planet was at superior conjunction, placing it on the opposite side of the sun from Earth. The closest approach on that flyby was about 1,800 miles (3,000 kilometers) of the planet's surface.

"Because of superior conjunction, because we knew we were going into radio blackout, and we knew we had the second flyby coming up in June, we elected not to turn on any of the Messenger instruments at the time of that flyby," said the mission's principal investigator, Sean Solomon of the Carnegie Institution of Washington.

The second Venus flyby marked the first time Messenger's full suite of scientific instruments was to be turned on simultaneously, allowing scientists to test and calibrate them before turning them onto their main planetary objective next January.

"The approach geometry is sufficiently similar to that of Mercury, allowing the seven instrument-package to be turned on and operating collectively in scientific observing mode, just as they will be for Mercury," Finnegan said.

Double-teaming Venus
Messenger was expected to collect more than 6 gigabytes of data about the Venus system and take more than 600 images during the 73-hour flyby. The information will provide new observations about Venus' atmosphere, cloud structure, space environment and perhaps even its surface.

During its brief encounter, Messenger was to make joint observations with a European spacecraft, Venus Express, that is currently in orbit around Venus. The two probes were programmed to work together to investigate how particles from the sun's solar wind affects and controls the upper layers of Venus's atmosphere.

"By coordinating and comparing these observations, we will be able to maximize the science from both missions and potentially learn things that would not be revealed by one set of observations alone," said study team member Ralph McNutt, also of the Applied Physics Laboratory.

Launched in August 2004, Messenger (which is actually an extended acronym for MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is the first mission to visit our solar system's innermost planet in more than 30 years, ever since NASA's Mariner 10 mapped about 45 percent of its surface. Messenger's mission is to map the entire planet, as well as gather information about Mercury's composition and structure, its geologic history, and the makeup of its core and poles.

This report was updated by

© 2013 All rights reserved. More from

Video: Messenger's roundabout journey


Discussion comments


Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments