ESA VEGA Payload: Italian satellite to help measure space-time warp

Payloads for Vega's first mission include LARES, ALMASat 1, and seven CubeSats from universities across Europe. Credit: ESA/CNES/Arianespace

Scheduled for launch from French Guiana on Monday, Europe's first lightweight Vega rocket is packed with nine small research satellites, including a unique Italian craft designed to help make an elusive accurate measurement of a central tenet of Albert Einstein's theory of general relativity.

The 98-foot-tall booster is due for liftoff in a two-hour launch window opening at 1000 GMT (5 a.m. EST) Monday.

The four-stage launcher, developed with Italian leadership, will make its first flight from the Guiana Space Center, a European-run spaceport in French Guiana.

The Vega rocket will deploy its nine payloads at different altitudes, first releasing the Laser Relativity Satellite about 55 minutes after launch in a circular 901 mile-high orbit with an inclination of 69.5 degrees.

Another firing by the Vega's fourth stage, powered by a Ukrainian liqiud-fueled engine, will reduce the altitude of the orbit's low point to 217 miles before deploying Italy's ALMASat 1 technology demonstration satellite and seven two-pound CubeSats built by learning institutions across Europe.

The Vega's mission will conclude 81 minutes after launch.

Officials selected LARES as the main passenger for the rocket's qualification flight, which aims to prove Vega's flight and ground systems before it is entrusted with more costly payloads on subsequent missions.

Carved out of a single ball of tungsten, LARES is covered 92 laser retroreflectors, allowing a network of ranging stations around the world to track the spherical satellite in orbit.

By bouncing laser signals off reflectors on LARES, scientists can precisely compute its position in space.

After comparing the actual location of LARES against predictions, researchers can measure the frame-dragging effect, part of Einstein's theory of general relativity which states that a rotating mass can distort space-time around it.

"Imagine the Earth as if it were immersed in honey. As the planet rotates, the honey around it would swirl, and it's the same with space and time," said Francis Everitt, a Standford University researcher who led the science team for NASA's Gravity Probe B mission, which confirmed the frame-dragging, or Lense-Thirring, effect at 37.2 milliarcseconds with a margin for error of about 19 percent.

Artist's concept of the frame-dragging effect around Earth. Credit: Stanford University

The frame-dragging effect manifests itself in minuscule changes in the orbits of satellites. Scientists observed two precursors to LARES, named LAGEOS 1 and LAGEOS 2, over several years to determine their orbital planes shifted 6 feet per year in the direction of Earth's rotation.

The LAGEOS tracking, coupled with a precise Earth gravity model, produced an estimation of the frame-dragging effect at 99 percent of the value predicted under general relativity.

The joint U.S.-Italian LAGEOS mission ultimately measured the effect with an accuracy of about 10 percent.

The objective of LARES is to refine the real effect of frame-dragging with an accuracy approaching 1 percent, according to the Italian space agency, which is funding the mission.

Better data on the frame-dragging effect around Earth will help astrophysicists study distant black holes, neutron stars and active galactic nuclei, whose immense gravity creates much stronger warping of space-time.