Spaceflight Now Home

The Mission

Rocket: Delta 2 (7920)
Payload: Gravity Probe-B
Date: April 19, 2004
Time: 1701 GMT (1:01 p.m. EDT)
Site: SLC-2W, Vandenberg Air Force Base, California
Satellite feed: AMC 9, Transponder 9, C-band

Spaceflight Now +

Premium video content for our Spaceflight Now Plus subscribers.

Gravity Probe-B preview
Scientists and mission officials preview the Gravity Probe-B project in this pre-flight news briefing from Friday, April 2. (62min 25sec file)
 Play video

Become a subscriber
More video


Sign up for our NewsAlert service and have the latest news in astronomy and space e-mailed direct to your desktop.

Enter your e-mail address:

Privacy note: your e-mail address will not be used for any other purpose.

Launch of Einstein space mission delayed

Posted: April 7, 2004; Updated April 8 with NASA statement

A technical glitch has forced managers to postpone by two days the long-awaited launch of NASA's Gravity Probe-B spacecraft that will check key aspects of Einstein's general theory of relativity.

"The additional time is necessary to allow engineers to troubleshoot an apparent short in launch pad ground support equipment," officials said in announcing the delay late Wednesday. "This equipment is needed for a safe and secure launch of the GP-B spacecraft."

The problem is associated with a spacecraft battery monitoring circuit.

"Without this circuit, the battery voltage on the spacecraft cannot be remotely monitored from the pad during certain essential operations," NASA said in a statement.

Liftoff atop a Boeing Delta 2 rocket from Vandenberg Air Force Base in California is now scheduled for Monday, April 19 at 1701 GMT (1:01 p.m. EDT; 10:01 a.m. local time).

The Gravity Probe-B spacecraft. Credit: Lockheed Martin/Russ Underwood
The satellite was delivered to the Space Launch Complex-2 West pad on Thursday, April 1.

Shrouded in a large transportation canister, Gravity Probe-B was driven to the seaside launch complex overlooking the Pacific, hoisted into the pad's tower and attached to the Delta 2 rocket's upper stage.

Moving to the launch pad marks an achievement for any launch campaign. But for Gravity Probe-B the milestone was doubly noteworthy since this $700 million NASA mission has a history dating back four decades, nearly as long as the space agency itself.

"It's already 150 feet off the ground so we are encouraged," quipped Rex Geveden, Gravity Probe-B program manager.

Once placed into a polar orbit 400 miles above Earth, Gravity Probe-B will carry out an exotic test of Albert Einstein's theories of space and time.

The satellite is equipped with four gyroscopes that serve as the heart of its experiment. Over the course of several months in space, scientists will look for very precise changes in the direction of spin of the four gyros as they provide an almost perfect space-time reference system.

The mission will test two predictions of Einstein's general theory of relativity: the "geodetic effect" of how space and time are warped by the presence of the Earth and "frame dragging" of how Earth's rotation drags space and time around with it.

We will post a comprehensive mission preview report next week. In addition, we will provide live play-by-play updates throughout the countdown and launch.