OrbitalHub

NASA dixit:

“LISA Pathfinder, a mission led by the European Space Agency (ESA) with contributions from NASA, has successfully demonstrated critical technologies needed to build a space-based observatory for detecting ripples in space-time called gravitational waves. Now a team of NASA scientists hopes to take advantage of the spacecraft’s record-breaking sensitivity to map out the distribution of tiny dust particles shed by asteroids and comets far from Earth.

Most of these particles have masses measured in micrograms, similar to a small grain of sand. But with speeds greater than 22,000 mph (36,000 km/h), even micrometeoroids pack a punch. The new measurements could help refine dust models used by researchers in a variety of studies, from understanding the physics of planet formation to estimating impact risks for current and future spacecraft.

The mission’s primary goal was to test how well the spacecraft could fly in formation with an identical pair of 1.8-inch (46 millimeter) gold-platinum cubes floating inside it. The cubes are test masses intended to be in free fall and responding only to gravity.

The spacecraft serves as a shield to protect the test masses from external forces. When LISA Pathfinder responds to pressure from sunlight and microscopic dust impacts, the spacecraft automatically compensates by firing tiny bursts from its micronewton thrusters to prevent the test masses from being disturbed.

In response to an impact, LISA Pathfinder fires its thrusters to counteract both the minute “push” from the strike and any change in the spacecraft’s spin. Together, these quantities allow the researchers to determine the impact’s location on the spacecraft and reconstruct the micrometeoroid’s original trajectory. This may allow the team to identify individual debris streams and perhaps relate them to known asteroids and comets.

Its distant location, sensitivity to low-mass particles, and ability to measure the size and direction of impacting particles make LISA Pathfinder a unique instrument for studying the population of micrometeoroids in the inner solar system. But it’s only the beginning.

LISA Pathfinder is managed by ESA and includes contributions from NASA Goddard and NASA’s Jet Propulsion Laboratory in Pasadena, California. The mission launched on December 3, 2015, and began orbiting a point called Earth-Sun L1, roughly 930,000 miles (1.5 million km) from Earth in the sun’s direction, in late January 2016. LISA stands for Laser Interferometer Space Antenna, a space-based gravitational wave observatory concept that has been studied in great detail by both NASA and ESA. It is a concept being explored for the third large mission of ESA’s Cosmic Vision Plan, which seeks to launch a gravitational wave observatory in 2034. “

Video credit: NASA

ESA dixit:

“Liftoff of Vega VV06 carrying LISA Pathfinder from Europe’s Spaceport, French Guiana, at 04:04 GMT/05:04 CET on 3 December 2015. Vega will place LISA Pathfinder into an elliptical orbit around our planet. Then, the spacecraft will use its own propulsion module to raise the highest point of the orbit in six stages. The last burn will propel the spacecraft towards its operational orbit, around a stable point called L1, some 1.5 million km from Earth towards the Sun.

Once on its final orbit, LISA Pathfinder will test key technologies for space-based observation of gravitational waves. These ripples in the fabric of spacetime are predicted by Albert Einstein’s general theory of relativity but have not yet been directly detected.

To demonstrate the fundamental approach that could be used by future missions to observe these elusive cosmic fluctuations, LISA Pathfinder will realize the best free-fall ever achieved in space. It will do so by reducing all the non-gravitational forces acting on two cubes and monitoring their motion and attitude to unprecedented accuracy.”

Video credit: ESA/Arianespace

Wikipedia dixit:

“LISA Pathfinder will place two test masses in a nearly perfect gravitational free-fall, and will control and measure their relative motion with unprecedented accuracy. The test masses and their environment will be the quietest place in the Solar System.

LISA Pathfinder is a proof-of-concept mission to prove that the two masses can fly through space, untouched but shielded by the spacecraft, and maintain their relative positions to the precision needed to realize a full-up gravitational wave observatory later. The primary objective is to measure deviations from geodesic motion. Much of the experimentation in gravitational physics requires measuring the relative acceleration between free-falling, geodesic reference test particles.

In LISA Pathfinder, precise inter-test-mass tracking by optical interferometry will allow scientists to assess the relative acceleration of the two test masses, situated about 38 cm apart in a single spacecraft. The science of LISA Pathfinder consists of measuring and creating an experimentally-anchored physical model for all the spurious effects – including stray forces and optical measurement limits – that limit the ability to create, and measure, the perfect constellation of free-falling test particles that would be ideal for the eLISA follow up mission. In particular, it will verify: drag-free attitude control of a spacecraft with two proof masses, the feasibility of laser interferometry in the desired frequency band (which is not possible on the surface of Earth), and the reliability and longevity of the various components—capacitive sensors, microthrusters, lasers, and optics.

For the follow-up mission, eLISA, the test masses will be 2 kg cubes housed in two separate spacecraft one million kilometers apart.”

Video credit: ESA