Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. 24/7 Space News .




SPACE SCOPES
The experts behind Gaia's arrival at nothingness
by Staff Writers
Paris (ESA) Jan 20, 2014


No ESA satellite reaches its destination without the 'spacecraft navigators' - the flight dynamics experts who predict and determine trajectories, prepare orbit manoeuvres and determine satellite attitudes and pointing. Image courtesy ESA/J. Mai.

With a final, modest, thruster burn yesterday afternoon, ESA's billion-star surveyor finalised its entry into orbit around 'L2', a virtual point far out in space. But how do you orbit nothing? And who can show you how to get there, anyway?

Just after 15:30 GMT (16:30 CET) yesterday, Gaia made a short thruster burn, nudging the galactic survey craft onto its planned scientific orbit. The job had been mostly completed last week, after an almost two-hour firing took Gaia into a squiggly path about the L2 Lagrange point, 1.5 million km from Earth.

But this apparently simple manoeuvre belies an astonishing fact: the L2 point consists of precisely nothing. It's simply a point in space.

Nothing there
"Lagrange points are special - it's true there's nothing there," says Markus Landgraf, a mission analyst at ESOC, ESA's operations centre 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."

As seen from this Lagrange point (there are a total of five such points in the Sun-Earth system), the Sun, Earth and Moon will always be close together in the sky, so Gaia can use its sunshield to protect its instruments from the light and heat from these three celestial bodies simultaneously.

This also helps the satellite to stay cool and enjoy a clear view of the Universe from the other side.

L2 provides a moderate radiation environment, which helps extend the life of the instrument detectors in space. However, orbits around L2 are fundamentally unstable.

"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.

For those used to seeing images of the International Space Station orbiting Earth, or Mars Express orbiting the Red Planet, it seems intuitive that spacecraft have to orbit something. How do you get a spacecraft to orbit around a point of nothingness?

ESA flight dynamics experts
To maintain this orbit for Gaia's planned 5-year mission requires extremely careful work by ESA's flight dynamics team - the experts who determine and predict trajectories, prepare orbit manoeuvres and determine satellite attitudes.

The flight dynamics experts use a range of software tools, developed and refined during decades of support to missions around Earth and across the Solar System.

To plan the orbit, the team applies mathematical models to generate an initial guess for the target orbit and how to get there. This guess must account for the requirements and constraints of the launcher and the needed telecommunications links.

Next, those initial guesses are fed into simulation software to see if the results would violate any of the constraints. Often, no solution is possible.

"That is where expertise and experience are indispensable to reconsider the assumptions and then start all over," says 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."

.


Related Links
Operations at ESA
Space Telescope News and Technology at Skynightly.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





UAV Payloads 2014, 24 - 25 June - London, UK
SPACE SCOPES
Hubble and Spitzer Team up to Probe Faraway Galaxies
Baltimore MD (SPX) Jan 10, 2014
NASA's Hubble and Spitzer Space Telescopes are providing a new perspective on the remote universe, including new views of young and distant galaxies bursting with stars. Scientists described the findings Tuesday in a news conference sponsored by the American Astronomical Society. The discoveries include four unusually bright galaxies as they appeared 13 billion years ago and the deepest im ... read more


SPACE SCOPES
NASA Seeks Partnership Opportunities For Commercial Lunar Landers

Chang'e-3 probe sets out on new missions

China's lunar probe observes stars, explores moon

China's moon rover performs first lunar probe

SPACE SCOPES
Mystery Mars rock reveals unexpected chemical composition

Mysterious stone 'rawled up' to Mars Rover Opportunity

Oppy Encounters A Surprise At Solander Point

Dutch researcher says Earth food plants able to grow on Mars

SPACE SCOPES
NASA Tests Orion Spacecraft Parachute Jettison over Arizona

New patent mapping system helps find innovation pathways

Working Together to Build Tomorrow's STEM Workforce

US Congress Rejects White House Cuts to Planetary Exploration

SPACE SCOPES
Official: China's space policy open to world

China launches communications satellite for Bolivia

China's moon rover continues lunar survey after photographing lander

China's Yutu "naps", awakens and explores

SPACE SCOPES
Cygnus Work Under Way, Normal Station Operations Continue

Spaceflight, Nanoracks Partnership Launch CubeSat Customers Towards Historic ISS Deployment

Orbital's cargo ship arrives at space station

Obama Administration Extends ISS Until at Least 2024

SPACE SCOPES
NASA Commercial Crew Partner SpaceX Tests Dragon Parachute System

NASA's Commercial Crew Partners Aim to Capitalize, Expand on 2013 Successes in 2014

Ariane Flight VA217; Ariane Flight VA216 and Soyuz Flight VS07

2014 set to be a very productive year for collaboration between Arianespace and Italy

SPACE SCOPES
First planet found around solar twin in star cluster

NASA's Kepler Provides Insights on Enigmatic Planets

Powerful Planet Finder Turns Its Eye to the Sky

New kind of planet or failed star? Astrophysicists discover category-defying celestial object

SPACE SCOPES
CCNY Team Models Sudden Thickening of Complex Fluids

Potential Future Data Storage at Domain Boundaries

What makes superalloys super - hierarchical microstructure of a superalloy

Quantum physics could make secure, single-use computer memories possible




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement