Gaia Spacecraft Enters Orbit Around Nothing

Lee Rannals for redOrbit.com – Your Universe Online

The European Space Agency’s (ESA) Gaia spacecraft made a final, modest adjustment yesterday afternoon to keep it on track for its orbit around nothing.

Gaia, which is being branded as ESA’s billion-star surveyor, finalized it’s entry into orbit around a virtual point far out in space known as L2. ESA said that Gaia made a short thruster burn on Tuesday to help nudge the spacecraft onto its planned scientific orbit around L2, which is essentially an orbit around nothing but a point in space.

“Lagrange points are special – it’s true there’s nothing there,” said Markus Landgraf, a mission analyst at ESOC, ESA’s operations center in Darmstadt, Germany. “They are points where the gravitational forces between two masses, like the Sun and Earth, add up to compensate for the centrifugal force of Earth’s motion around the Sun, and they provide uniquely advantageous observation opportunities for studying the Sun or our Galaxy.”

L2 allows the perfect position so Gaia can use its sunshield to protect its instruments from the light and heat of the Sun, Earth and Moon simultaneously. This will allow Gaia to stay cool while also getting a clear view of the Universe. ESA said that L2 provides a moderate radiation environment, helping to extend the life of the instrument detectors in space.

“We’ll have to conduct stationkeeping burns every month to keep Gaia around L2, otherwise perturbations would cause it to ‘fall off’ the point,” says Gaia Operations Manager David Milligan.

In order for Gaia to maintain its orbit around nothing for its 5-year primary mission, ESA’s flight dynamics team must be precise in preparing orbit maneuvers and satellite attitudes. These experts will have to use a range of software tools, developed and refined during decades of support to missions around Earth and across the Solar System.

ESA said the Gaia team will have to apply mathematical models to generate an initial guess for the target orbit and how to get there. These guesses must account for the requirements and constraints of the launcher and the needed telecommunications links. They must also use simulation software to determine whether the results would violate any of the constraints.

“That is where expertise and experience are indispensable to reconsider the assumptions and then start all over,” said Frank Dreger, head of Flight Dynamics. “There’s no commercial source for this sort of software or expertise – it’s been built up over many years at ESOC and represents a capability that is rare in the world and unique in Europe.”