A European consortium submitted to ESA in January a proposal for the development of the Laser Interferometer Space Antenna (LISA) mission for ESA’s third large mission, or L3, competition. LISA is widely considered the leading candidate to be selected for that mission for launch likely in the early 2030s.LISA, as proposed, will consist of three spacecraft in a triangular formation, each 2.5 million kilometers from the other two in an orbit around the sun trailing the Earth. The spacecraft would shine lasers at each other, with interferometers on each spacecraft detecting minute distance changes caused by passing gravitational waves.The three spacecraft, with a combined mass of about 6,000 kilograms, including payload adapter, would launch on an Ariane 6 and drift to their planned orbit over the course of a year and a half. LISA would have a planned mission lifetime of four years, but with sufficient propellant on each spacecraft to operate for up to a decade.“LISA looks like it’s going to happen. It looks like it’s on a pretty firm track,” said David Shoemaker, a senior research scientist at the Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Research, during a meeting of the American Physical Society (APS) here Jan. 29.Shoemaker is chairman of the L3 Study Team, a NASA group looking at contributions NASA can make to the LISA mission. The LISA proposal submitted to ESA assumes NASA will cover 20 percent of the mission’s cost through instruments and other technologies.Parth of the confidence of Shoemaker and other scientists is linked to the announcement a year ago of the first detection of gravitational waves, by the Laser Interferometer Gravitational-Wave Observatory (LIGO), ground-based gravitational wave detectors in Louisiana and Washington. That discovery removed any doubt that gravitational waves exist, creating confidence that a mission like LISA could also successfully detect and study gravitational waves, and do so at frequencies not possible with LIGO.Another factor is the technical success of ESA’s LISA Pathfinder mission, a single small spacecraft launched in December 2015 to test technologies that could be used in a later LISA mission. The performance of the spacecraft, including a thruster system provided by NASA, exceeded expectations.Those tests not only exceeded the stability expectations of the LISA Pathfinder mission, but also approached the requirements for the full-fledged LISA mission. “This was a successful demonstration of drag-free control at a level necessary for a LISA-type gravitational wave observatory,” said Charles Dunn of JPL, project technologist for the disturbance reduction system flown on LISA Pathfinder, at the APS meeting Jan. 28.
After sixteen months of science operations, LISA Pathfinder will complete its mission on 30 June, having successfully demonstrated the technology to build ESA's future space observatory of gravitational waves.
As LISA Pathfinder approaches the end of its successful technology demonstration mission, ESA's Science Programme Committee has selected today the Laser Interferometer Space Antenna (LISA) as the third large mission (L3) in ESA's Cosmic Vision plan. LISA is a space-based observatory of gravitational waves consisting of a constellation of three spacecraft, with launch planned for 2034.
LISA Pathfinder operations were split between the two experiments. Both thruster technologies have now been validated and will benefit future space projects such as large space observatories, or missions involving multiple spacecraft flying in formation.The mission will continue taking data until 30 June, with a final experiment that will be pushing the precision limits of the test mass grabbing and releasing mechanisms – something of great importance for LISA. Then, after a series of final operational tests, the last command will be sent on 18 July.A preliminary de-orbiting manoeuvre was already performed in April, nudging the spacecraft away from its orbit around the first Sun-Earth Lagrange point, L1, and towards a long-term stable parking orbit around the Sun.
On 18 July, the LPF mission will conclude with the final commands sent to switch off the on-board transmitter. Since April, the mission operations team in Darmstadt have been working to ensure a safe and smooth end-of-life for this fantastic technology demonstration spacecraft.
For disposal, the spacecraft has already performed a de-orbit manoeuvre to leave its Lagrangian orbit and start to drift ahead of the Earth in a heliocentric orbit around the Sun. The spacecraft now has an orbital period a few days shorter than that of the Earth, keeping the spacecraft safely out of the way and drifting serenely around the Sun.
30 June marked the end of the science mission ...
LISA PATHFINDER: BAKE, RATTLE AND ROLL13 July 2017The final days of the LISA Pathfinder mission are some of the busiest, as controllers make final tests and get ready to switch off the gravitational pioneer next Tuesday.Following 16 months of scientific effort, LISA Pathfinder completed its main mission on 30 June, having demonstrated the technology needed to operate ESA’s future LISA space observatory to study gravitational waves – ripples in spacetime predicted by Albert Einstein in his General Theory of Relativity.The LISA mission will comprise three spacecraft orbiting some 2.5 million km apart in a triangular formation, with their ‘test masses’ isolated from all external forces bar gravity and linked by laser beams.With the required sensitivity fully proven by LISA Pathfinder, teams are now using the spacecraft’s last days to conduct a series of technical tests on components and devices, making full use of every remaining minute.“These tests will give us a better grasp of the craft’s behaviour and provide valuable feedback to the manufacturers about the characteristics of their equipment, in both routine and unusual conditions,” says spacecraft operations manager Ian Harrison.“The gravitational wave detectors work by measuring the changing separation of two cubes that are in free-fall. Changes in the spacecraft’s state or any movement may interfere with the measurements, and we want to better understand these for the future mission.”In addition to satellite movement, the delicate cubes on LISA Pathfinder can be influenced by variations in their environment, such as in temperature and magnetic interference.Baking, rattling and rollingWorking at ESA’s mission control centre in Darmstadt, Germany, the controllers have been conducting daily tests since the mission formally ended its normal phase on 30 June. These could not be performed before because meeting the science goals required a very stable and ‘quiet’ environment.Engineers have commanded the craft to turn to assess thermal effects on its systems, particularly the micropropulsion system, from solar illumination.Repeating thermal tests previously performed on the ground will help to improve procedures for the future LISA mission.Other tests are analysing the effect of magnetic interference, from the operation of pressure regulation valves in the cold-gas thruster system, on the spacecraft’s magnetic momentum, external forces and test mass control.The teams have also been pushing the micropropulsion system and test-mass electrostatic sensing and control systems to their limits.Spacecraft performance data have been recorded since the time of launch in December 2015 up to these last experiments, to determine the rate of hardware degradation in the harsh environment of space.Boosting European industryResults from this test series will be available to European hardware manufacturers for incorporation into future designs.“These tests will help to eliminate variables that might influence the science results from future ESA missions, such as Euclid and LISA, and help reduce risk in their development,” says flight director Andreas Rudolph.“The tests could go wrong for many reasons and might cause loss of data, or adversely affect the spacecraft, so they were not considered during the main technology demonstration phase of the mission.“This is a great opportunity to test hardware in flight, with no effect on the mission objectives or final activities.”Ready for lights outGround teams are getting ready to ‘passivate’ LISA Pathfinder, eliminating radio transmissions from the spacecraft and switching off most of the units.In April, the spacecraft used its thrusters over five days to nudge itself into a safe orbit around the Sun, minimising any probability that it will return to the vicinity of Earth or Moon in the next 100 years, in line with ESA's requirement for space debris mitigation.The final command switching off the craft is planned for around 18:00 GMT on 18 July.“Before LISA Pathfinder, gravitational wave astronomy from space was a theoretical possibility, with its future implementation hidden behind a thick, dark wall,” says ESA’s Paolo Ferri, head of mission operations.“This mission has opened a ‘door’ in this wall. The road to achieving a future mission that will detect gravitational waves is still very long, but we can see it and we can now start planning our long journey to reach it.”
Today, teams will dump & wipe accumulated hardware test data frm onboard memory - make room for end-of-mission commands #eom #LISAPathfinder
Later, #LISAPathfinder will be commanded to spin up - to further understand its behaviour when manoeuvring #LISAPathfinder
Update from LISAPathfinder Operations Manager Ian Harrison at ESOC: Today's in-orbit spin-up test postponed. There has been an increase in solar activity, so there's a last-min request to resume LISAPathfinder 'science mode' & measure charge build-up on the test masses. The team are also repeating the low-pressure test on the Cold Gas Thruster system down to 0.2bar. Busy final days! LISAPathfinder proving to be a valuable mission right to the end! Last command 20:00CEST 18.07
After days of suspenseful quiet, huge sunspot AR2665 finally erupted on July 14th (0209 UT), producing a powerful and long-lasting M2-class solar flare. Extreme ultraviolet telescopes onboard NASA's Solar Dynamics Observatory recorded the blast. Remarkably, the explosion persisted for more than two hours, producing a sustained fusillade of X-rays and energetic protons that ionized the upper layers of Earth's atmosphere. Shortwave radio blackouts were subsequently observed over the Pacific Ocean and especially around the Arctic Circle. Of even greater interest is the coronal mass ejection (CME). The explosion hurled a bright CME away from the blast site, and it appears to be heading for Earth. This expanding cloud will likely reach our planet on July 16th, possibly sparking geomagnetic storms and high-latitude auroras when it arrives.
ESA Operations Verified account @esaoperations 2m2 minutes ago#LISAPathfinder last command transmitted today ~20:00CEST - follow via Facebook live starting 19:45CEST https://www.facebook.com/EuropeanSpaceAgency/
Published on 18 Jul 2017The LISA Pathfinder mission ends on 18 July 2017 after a successful demonstration of the technology needed to detect gravitational waves in space. These vibrations in spacetime, first predicted by Einstein over a hundred years ago, are produced by huge astronomical events - such as two black holes colliding - and will allow scientists to open new windows into our universe.The success of the LISA Pathfinder mission has paved the way for the newly selected LISA mission which, when built and launched, will detect gravitational waves from objects up to a million times larger than our Sun.The film features interview soundbites from Dr Paul McNamara, LISA Pathfinder Project Scientist, at the European Space Agency’s European Technology and Science facility (ESTEC) in The Netherlands.
ESA Operations Verified account @esaoperations 9m9 minutes agoWe have #AOS! #LISAPathfinder controllers established contact with their craft for the last time just after 16:00CEST
Update from the Main Control Room: A-chain of #LISAPathfinder's redundant on-board systems now OFF & craft is flying on its B-chain.