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LISA Pathfinder scheduled to launch tomorrow, 2015-12-01
LISA Pathfinder -- a technology-demonstrator mission for the proposed
eLISA space-based gravitational-wave detector -- is scheduled to launch tomorrow (1 December 2015), at 11:15pm US-Eastern time. For more on eLISA and LISA Pathfinder see https://en.wikipedia.org/wiki/Evolve..._Space_Antenna https://en.wikipedia.org/wiki/LISA_Pathfinder Quoting from a recent E-mail from Ann Hornschemeier at NASA, LISA Pathfinder is scheduled to launch -tomorrow- December 1st at 11:15PM Eastern time. ** For live streaming of the launch, there are two options: * Ariane Space: http://www.arianespace.tv/ * ESA TV: http://www.esa.int/esatv/Transmissio..._Vega_V06_Live *** For more information on LISA Pathfinder launch events and activities: There is a new website (lisapathfinder.org http://lisapathfinder.org/) provided by the eLISA Consortium *** For more information on LISA Pathfinder in general: "Official" ESA website: ESA Science Site: http://www.cosmos.esa.int/web/lisa-pathfinder Twitter: @ESA_LPF, @esascience, @arianespace, #lisapathfinder, #VV06 Facebook: https://www.facebook.com/lpf.lisapathfinder/about ciao, -- -- "Jonathan Thornburg [remove -animal to reply]" Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA "There was of course no way of knowing whether you were being watched at any given moment. How often, or on what system, the Thought Police plugged in on any individual wire was guesswork. It was even conceivable that they watched everybody all the time." -- George Orwell, "1984" |
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LISA Pathfinder scheduled to launch tomorrow, 2015-12-01
On 11/30/15 2:00 PM, Jonathan Thornburg [remove -animal to reply] wrote:
LISA Pathfinder -- a technology-demonstrator mission for the proposed eLISA space-based gravitational-wave detector -- is scheduled to launch tomorrow (1 December 2015), at 11:15pm US-Eastern time. 'Delayed till 3 December' It will be interesting to see if LISA Pathfinder will observe 10^-4 to 10^-5 Hz frequencies as observed by Gravity Probe B gyros. RDS [[Mod. note -- 1. LISA Pathfinder is an engineering test mission containing an interferometer with a ~50cm armlength, not a gravitational-wave observatory with a multi-million-km armlength. Because gravitational-wave sensitivity is roughly proportional to armlength, LISA Pathfinder won't have any scientifically-interesting gravitational-wave sensitivity. Rather its purpose is to test and demonstrate various engineering subsystems (e.g., very-low-noise interferometers, interferometric measurement with picometer sensitivity, vibration control, drag-free control systems, microNewton thrusters, etc etc) which can then be applied to the eLISA mission (or even a resurrected LISA if someone comes up with a spare 0.5e9 or so dollars/Euros) mission. 2. LISA had peak sensitivity at frequencies of a few mHz; eLISA is currently planned to have peak sensitivity at slightly frequencies, maybe around 10 mHz. eLISA won't be very sensitive at the 10-100 microHz frequencies you mention. 3. Gravity Probe B didn't observe gravitational waves at any frequency. Rather it (using those super-low-noise gyros, and various other fancy technologies) observed (a) geodetic precession due to the satellite orbiting the Earth, and (b) Lenz-Thirring frame-dragging due to the Earth being spinning -- jt]] |
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LISA Pathfinder scheduled to launch tomorrow, 2015-12-01
On 12/2/15 3:09 AM, Richard D. Saam wrote:
On 11/30/15 2:00 PM, Jonathan Thornburg [remove -animal to reply] wrote: LISA Pathfinder -- a technology-demonstrator mission for the proposed eLISA space-based gravitational-wave detector -- is scheduled to launch tomorrow (1 December 2015), at 11:15pm US-Eastern time. 'Delayed till 3 December' It will be interesting to see if LISA Pathfinder will observe 10^-4 to 10^-5 Hz frequencies as observed by Gravity Probe B gyros. RDS [[Mod. note -- 1. LISA Pathfinder is an engineering test mission containing an interferometer with a ~50cm armlength, not a gravitational-wave observatory with a multi-million-km armlength. Because gravitational-wave sensitivity is roughly proportional to armlength, LISA Pathfinder won't have any scientifically-interesting gravitational-wave sensitivity. Rather its purpose is to test and demonstrate various engineering subsystems (e.g., very-low-noise interferometers, interferometric measurement with picometer sensitivity, vibration control, drag-free control systems, microNewton thrusters, etc etc) which can then be applied to the eLISA mission (or even a resurrected LISA if someone comes up with a spare 0.5e9 or so dollars/Euros) mission. 2. LISA had peak sensitivity at frequencies of a few mHz; eLISA is currently planned to have peak sensitivity at slightly frequencies, maybe around 10 mHz. eLISA won't be very sensitive at the 10-100 microHz frequencies you mention. 3. Gravity Probe B didn't observe gravitational waves at any frequency. Rather it (using those super-low-noise gyros, and various other fancy technologies) observed (a) geodetic precession due to the satellite orbiting the Earth, and (b) Lenz-Thirring frame-dragging due to the Earth being spinning -- jt]] Gravity Probe B did establish (a) and (b) but in the process its super-low-noise gyros did observe anomalous 10-100 microHz frequencies having a particular harmonic pattern. (in tune with a universe source?) Alex Silbergleit, John Conklin and the Polhode/Trapped Flux Mapping Task Team, Hansen Experimental Physics Laboratory(HEPL) Seminar, Polhode Motion, Trapped Flux, and the GP-B Science Data Analysis, July 8, 2009, Stanford University. The super-low-noise gyros incorporated niobium superconducting material introducing an unknown/unanticipated contributor to the experiment. The anomalous 10-100 microHz frequencies were brushed away with subsequent computer finesse. ESA graphics indicate some 10-100 microHz frequency sensitivity. Is it enough sensitivity to replicate those anomalous Gravity Probe B 10-100 microHz frequencies? RDS [[Mod. note -- I think it would be very hard to make a solid case that a substantial part of Gravity Probe B's noise was due to gravitational waves (as opposed to various other noise sources within the Gravity Probe B spacecraft). That said, the full eLISA mission should have fairly good sensitivity at 10-100 microHz (probably limited by "confusion noise" from the large number of unresolved close-white-dwarf binaries in our galaxy). I don't think LISA Pathfinder will have any scientifically useful gravitational- -wave sensitivity. -- jt]] |
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LISA Pathfinder scheduled to launch tomorrow, 2015-12-01
On Thursday, December 3, 2015 at 2:02:32 AM UTC-5, Richard D. Saam wrote:
[[Mod. note -- 70 excessively-quoted lines snipped here. -- jt]] [[Mod. note -- I think it would be very hard to make a solid case that a substantial part of Gravity Probe B's noise was due to gravitational waves (as opposed to various other noise sources within the Gravity Probe B spacecraft). That said, the full eLISA mission should have fairly good sensitivity at 10-100 microHz (probably limited by "confusion noise" from the large number of unresolved close-white-dwarf binaries in our galaxy). I don't think LISA Pathfinder will have any scientifically useful gravitational- -wave sensitivity. -- jt]] If memory servers liquid helium splashing around was another variable that had to be massaged out of the B probe data. Not sure how liquid helium could splash around without a gravity gradient but apparently it did. As helium depleted the frequency changed which was a red flag that this was a liquid helium resonate splashing problem. A 1 meter length with a positive charge on one side and a negative charge on the other. A gravity wave would change the distance between the negative and positive charges. Theoretically this should translate a gravity wave into an electromagnetic wave. However this would be limited to gravity waves in the 200 MHz range with only a 1 meter length. There is theory and there are measurements made. The common AM radio with a sensitivity of 10 u volts , 10e-6 V , can receive EM waves in the 1 MHz range with a ferrite antenna that is less than .01 percent of the EM wave length of 1 MHz. 1 MHz wave length is a few city blocks long but the ferrite antenna is only 2 or 3 inches long. It is possible we already have the technology , radio , to measure gravity waves in a more efficient way if a gravity wave could be translated into a EM wave such as the example of a positive and negative charge placed 1 meter apart in the path of a gravity wave. [[Mod. note -- Unfortunately, detecting gravitational waves is MUCH harder than detecting radio waves. [It's best to refer to "gravitational waves", not "gravity waves", because the latter term already has a well-established and quite different meaning, referring to (e.g.) the usual waves one sees on the surface of the Earth's ocean.] Roughly speaking, detecting gravitational waves is about as hard as detecting radio waves would be if the only materials we had available from which to construct our radio antenna were different types of wood. More quantitatively, we expect any gravitational waves here on Earth to be VERY weak, corresponding to a fractional change in the distance between those two test bodies of much less than 1 part in 10^20. That means we (a) a VERY sensitive measurement of the distance between the test bodies, and (b) a VERY low level of background noise. (b) in turn means that we want our test bodies to be electrically neutral and non-magnetic, so as to minimize the effects of any stray electromagnetic fields. -- jt]] |
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LISA Pathfinder scheduled to launch tomorrow, 2015-12-01
On 1/16/16 9:40 PM, John Heath wrote:
On Thursday, December 3, 2015 at 2:02:32 AM UTC-5, Richard D. Saam wrote: [[Mod. note -- 70 excessively-quoted lines snipped here. -- jt]] [[Mod. note -- I think it would be very hard to make a solid case that a substantial part of Gravity Probe B's noise was due to gravitational waves (as opposed to various other noise sources within the Gravity Probe B spacecraft). That said, the full eLISA mission should have fairly good sensitivity at 10-100 microHz (probably limited by "confusion noise" from the large number of unresolved close-white-dwarf binaries in our galaxy). I don't think LISA Pathfinder will have any scientifically useful gravitational- -wave sensitivity. -- jt]] If memory servers liquid helium splashing around was another variable that had to be massaged out of the B probe data. Not sure how liquid helium could splash around without a gravity gradient but apparently it did. As helium depleted the frequency changed which was a red flag that this was a liquid helium resonate splashing problem. Some type of Gravity Probe B splashing is evident, but was it helium or the actual gyro niobium superconductor 'fluid' medium at an estimated density of 8x10^-6 g/cc? But the question remains: what oscillating gravitational gradient could cause such? Alex Silbergleit, John Conklin and the Polhode/Trapped Flux Mapping Task Team, Hansen Experimental Physics Laboratory(HEPL) Seminar, Polhode Motion, Trapped Flux, and the GP-B Science Data Analysis, July 8, 2009, Stanford University. https://einstein.stanford.edu/RESOUR...ilbergleit.pdf 1. Asymptotic Polhode Period and Dissipation Time (and calculated harmonics after equilibrating Dissipation Time 'months') / Asymptotic Asymptotic Asymptotic Asymptotic / Polhode Polhode Polhode Polhode / Period Frequency Harmonic Harmonic / (hours) (Hz) Deviation Gyro 1 0.867 3.20E-04 9 1.05 Gryo 3 1.529 1.82E-04 5 1.08 Gyro 2 2.581 1.08E-04 3 1.06 Gyro 4 4.137 6.71E-05 2 0.99 Universe? 8.22 3.38E-05 1 1.00 The LISA-pathfinder free fall test masses described at http://sci.esa.int/lisa-pathfinder/5...sa-pathfinder/ are sensitive to 10^-3 to 10^-1 Hz and may detect the Gravity Probe B observed Universe? oscillating gravitational gradient at high (10) harmonics. What is the actual mass(g) of the test mass cubes? ESA is not looking for this anomalous effect on this LISA test run but its experimental appearance could be evident. Richard D Saam |
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