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Space Physics

Space Physics. Peter Fisher. Working in space - getting there is half the fun Experiments Just plain cool - the Tethered Satellite A long march - Gravity Probe B “Somebody’s gotta do it” - Alpha Magnetic Spectrometer Looking for a jerk - SNAP. Three big problems in space The ride uphill

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Space Physics

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  1. Space Physics Peter Fisher Peter Fisher - MIT

  2. Working in space - getting there is half the fun • Experiments • Just plain cool - the Tethered Satellite • A long march - Gravity Probe B • “Somebody’s gotta do it” - Alpha Magnetic Spectrometer • Looking for a jerk - SNAP Peter Fisher - MIT

  3. Three big problems in space • The ride uphill • Keeping cool • Telemetry Peter Fisher - MIT

  4. Rocket equations: The ride uphill Vesc=8,000 m/s 31 MJ per kg into orbit • Consequences: • Must minimize mass • High thrust: high vibration environment • Reduce drag: small payload Peter Fisher - MIT

  5. Pegasus (Orbital Sciences) Space shuttle Aerobee (USAF) Sea Launch (Boeing) Supergun (US Army) Delta IV (Boeing) Peter Fisher - MIT

  6. Delta IV Rocket 12,757 kg to orbit 1.5 m diameter shroud ~$3,000/kg No crew No repair, deployment Lower safety req. Frequent launch Space Shuttle 29,000 kg to LEO 2.8 m diameter payload bay ~$5,000/kg Crew Repair, deployment Very high safety Grounded! Access to ISS, or 14 day mission Peter Fisher - MIT

  7. Keeping cool - a question: Shuttle: 7 crew @ 100 W each Avionics - 2000 W How do you get rid of waste heat in space? Peter Fisher - MIT

  8. Stephan-Boltzmann: • Prad=(57nW/m2-K4)T4 • 461 W/m2 @ 300K • Solar cells: • Efficiency: 10-20% • Solar constant: 1.4kW/m2 • Pcell=140-280W/m2 Peter Fisher - MIT

  9. To keep cool: • Need 1 m2 of radiator for every 2 m2 of solar cells • Thermal management • system • Limit power Radiator with freon loop Peter Fisher - MIT

  10. Telemetry Space experiments always assume that communications may be lost (“comm-out”) at any time for an unknown duration. In typical orbits, there are frequently comm-out factors of 10 (Shuttle)-40(ISS)% Major implications… Peter Fisher - MIT

  11. Minimize data transmission, maximize on-board processing (subject to weight, power, thermal, etc.) 2Mb/sec. ave. All systems must go into safe mode during comm-out • 3. Find an alternate data path • 4. On-broad storage Peter Fisher - MIT

  12. AMS DAQ: 600 processors, 2kW ISS High Rate Coverage: 60%, Removable disks inside Peter Fisher - MIT

  13. B Just plain cool: the Tethered Satellite System: Concept A conductor moving through a magnetic field generates a potential V=El=F/q=vB/c Between the ends. For low Earth orbit: v=8,000 m/s B=0.3G l=20 km v V,l E=8mV/m V=4,800V Peter Fisher - MIT

  14. B je je je je Can generate EMF if There is a current return path (space plasma Magnet flux changes (orbit through dipole) Naïve calculation: EMF=(1/c)(dF/dt)=(1/c)A(dB/dt) ~(20 km)2(0.3 G/1000 sec.)/c ~12 V Space plasma plays a role; Parker-Murphy theory v V,l Peter Fisher - MIT

  15. Thethered Satellite System (TSS-1) - NASA/ASI joint project Deployable satellite with 5N thruster at the end of 20 km conducting tether deployed perpendicular to magnetic field. Generate power, measure space plasma properties. Peter Fisher - MIT

  16. TSS-1: jammed after deploying 300m TSS-1R: tether broke after 19.7 km, was generating 300W at time of separation. Feasible method of power generation, extracts energy kinetic energy of orbiter. Orbit lifetime> 1My. Peter Fisher - MIT

  17. A long march - Gravity Probe B The Lense-Thirring effect (1918) Rotating mass gives rise to “gravitomagnetic” field and • An object with angular momentum l will precess at rate • a- semi-major axis of orbit • e - eccentricity Peter Fisher - MIT

  18. To measure frame dragging, need • Gyroscope system (provides l) • A way of measuring precession • Apparatus in orbit around large mass (Earth) • Gravity Probe B (1974) • Four high precision spheres on two axis act as gryoscopes • Gyros coupled to freely floating telescope, measure deflection from a target star during orbit around Earth (3 y). Peter Fisher - MIT

  19. Pilot study starts in 1964 • Launch on 20 April 2004 • Instrument checkout complete, 20 July 2004. Science starts! http://gravityprobeb.com Peter Fisher - MIT

  20. “Somebody’s gotta do it” - AMS • Fritz Zwicky (1933): Galactic dynamics • Rotation curves • Cluster infall velocities • Perpendicular velocities • Lensing • By “Dark Matter”, I mean • g=0.15-0.60 GeV/cm3 • No strong or EM interactions • Vave=250 km/s Peter Fisher - MIT

  21. Peter Fisher - MIT

  22. 50 GeV Peter Fisher - MIT

  23. Integrated positron signal above 8 GeV for 10 GeV (solid line) and 30 GeV (dotted line). The Earth is located at 8.5 kpc radius. Peter Fisher - MIT

  24. Charged particles follow magnetic field lines Peter Fisher - MIT

  25. Magnetic turbulence - average variation of magnetic field: Mean time between scattering from inhomogenieties: Peter Fisher - MIT

  26. 30 GeV electron: v=c, gives average velocity along field c/31/2 Electron lifetime determined by time to to propagate one Xo=65 g/cm2 in hydrogen 1 proton/cm3 in ISM Xo=1.3 x 1013 kpc to=45 My Peter Fisher - MIT

  27. Number of scatterings: N=to/ts Random walk diffusion distance Diffusion coefficient Advance each step RMS number of steps Peter Fisher - MIT

  28. Charged particle spectrometers In ~10 GeV region: p:e-:e+ 103:10:0.1 p:p 103:0.1 High Energy Antimatter Telescope (Balloon) AMS-02 Peter Fisher - MIT

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  30. AMS-02 will just nail this Questions Why use e+/e++e-? Solar modulation not important above 10 GeV. Same signal appears in e-, so why not use e+, e-,… in combined fit? AMS-01 took LOTS of e- data (easy to ID, no p!) Why not look at that? Peter Fisher - MIT

  31. First glance at AMS-01 data (backgrounds, resolution not well understood yet). Need to do a lot of work (Gian-Paolo, Gray) Peter Fisher - MIT

  32. Bumps and Bangs: Terrestrial and solar capture Peter Fisher - MIT

  33. E nDM E-DE Maximum when =1, E=DE Most efficient energy transfer Peter Fisher - MIT

  34. 24Mg 28Si 32S 16O 56Fe, 58Ni Capture rate for Earth Peter Fisher - MIT

  35. Capture rate for Sun is ~108 times higher. Since Sun is mostly protons, no peaks and no strong suppression for Majorana type DM Earth Sun (scaled by 5 108 Peter Fisher - MIT

  36. Signal is SM neutrino flux from • The sun • The Earth • The center of the galaxy Detectors: SuperK (Kate, last week), AMANDA, ICECubed (Jody, Feb.), ANTERES Peter Fisher - MIT

  37. g M2 + M2 g gB gq Peter Fisher - MIT

  38. Looking for jerks - SuperNova Acceleration Probe (SNAP) Type Ia SN may be calibrated so the brightness is known independently of the distance from Earth. The large scale structure of the universe may be determined by plotting redshift vs. magnitude (distance). Peter Fisher - MIT

  39. Ho = Hubble expansion parameter qo=acceleration parameter jo=jerk parameter qo and jo depend on the matter content of the universe Peter Fisher - MIT

  40. Peter Fisher - MIT

  41. Peter Fisher - MIT

  42. The difficulty lies in finding the supernova early on. Need to measure the light output in several spectral bands as a function of time. Typically, use a survey telescope to find the SN, a spectrograph to measure z and a high resolution telescope to measure light output as a function of time. The major argument is whether this is an artisinal or industrial endeavor. Peter Fisher - MIT

  43. Industrial approach - orbiting observatory with all three instruments. Peter Fisher - MIT

  44. Other major endeavors in the coming years: • JWST - second generation Hubble Space Telescope, 6 m aperture • GLAST - gamma ray observatory, ten times EGRET, launch 2006 • LISA - constellation of three satellites, long baseline gravity wave detection • OWL/AirWatch - optical sensor satellite to observe cerenkov radiation from high energy cosmic rays in Earth’s atmosphere • Plank - next generation of cosmic background radiation measurement, <1o resolution, polarization, 2009 Peter Fisher - MIT

  45. Summary • Space provides access to fundamental cosmological (SN, CMB) and astrophysical (charged cosmic rays, gamma rays, neutrinos) which impact particle physics. Space is a very challenging place to try to mount an experiment: • Extreme engineering • Extreme political considerations (c.f. Presidential speech of Jan. 14, 2004) Peter Fisher - MIT

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