NASA’s Great Observatories!

1. NASA’s Great Observatories! By Matt Bartkowicz Tessa Stranik

2. NASA’s four Great Observatories

3. Hubble Space Telescope • Launched in April 1990 • The only one of the great observatories that are able to be serviced by shuttle missions • This makes upgrades with new scientific instruments possible • Detects radiation from 1200 Å to 2.4 μm (UV to near IR) • Hubble is in LEO

4. Aperture door Solar arrays Antennae Gyros Magnetic torquers Cameras and corrective optics Batteries

5. HST • The solar panels are actually the third pair on HST. • They are ⅓ smaller but produce 30% more power than the first ones (2400W) • Smaller size also reduces atmospheric drag

6. HST • Antennae transmits data and receives directions for science missions • In contact at Space Telescope Operations Control Center (STOCC) in Greenbelt, Maryland

7. HST • Aperture door protects optics when not in use • Light travels down the main baffle which also blocks stray light • Reflects off primary mirror, then secondary, then reaches the focal plain

8. HST • The pointing control system is designed to maintain .01 arcsec accuracy for 24 hours. • Fine Guidance Sensor - locks onto two guide stars • Fixed Head Star Tracker - locks onto a star in the field of view • Coarse Sun Sensor - tracks the sun and decides if aperture door needs to close • Magnetometer - measures position relative to the Earth’s magnetic field • Reaction Wheels - gyros that rotate or brake to transfer momentum and turn Hubble • Magnetic Torquers - Use Earth’s magnetic field to dump momentum from reaction wheels

9. HST • Contains four cameras and the corrective optics (for spherical aberration in primary mirror) • ACS (Advanced Camera for Surveys) • NICMOS (Near Infrared Camera and Multi-Object Spectrometer) • STIS (Space Telescope Imaging Spectrograph) • WFPC2 (Wide Field/Planetary Camera 2)

10. HST The Hubble Deep Field found many galaxies at high redshift that would have been difficult to detect from the ground and without Hubble wouldn’t have enough resolution to differentiate them from red stars. Because of this, the Hubble Ultra Deep Field was done. This doubled the exposure time from .5 million seconds to 1 million seconds. The HUDF reinforces the HDF conclusion that galaxies evolved strongly in the first couple billion years of the universe. Going back to z = 5-7, it also shows that there is not much difference between galaxies in that range and galaxies at z = 4 except for the number density. Also, star formation was happening in the earliest epochs we can observe. Another study used type Ia supernova to extend the Hubble diagram. It also found that luminosity distances were larger than expected for an empty universe, indicating a cosmological constant and/or dark energy have been accelerating the expansion of the universe. They found: ΩΛ= 0.71 ΩM = 0.29

11. Spitzer Space Telescope • Launched in August 2003 • Launched with Delta 7920H ELV from Cape Canaveral • Contains 360 Liters of liquid He • Able to do imaging from 3 to 180 μm, spectroscopy from 5-40 μm, and spectrophotometry from 50-100 μm • Spitzer is in a heliocentric orbit trailing Earth

12. Solar Panel Shield Solar Panel Helium Tank Telescope Nitrogen Tank Spacecraft Shield Antennae and Tracking System

13. SST • Very important to stay cold • Liquid He keeps telescope assembly cold • He vapor cools shell and shields, but also used as low thrust vents • Shell radiates heat to anti-sun side

14. SST • Light travels down baffle, off primary, off secondary and into the focal plane • Material made mostly of Beryllium to minimize thermal expansion mismatches and it has low specific energy

15. SST • Solar Panels convert the sun’s radiation to 427W of electricity • 50% reflectors to keep the panel from getting too hot • The panels are in a wedge shape around the shield to get a better view factor of space and reradiate extra energy

16. SST MIPS (Multiband Imaging Photometer for Spitzer) - Has arrays able to detect 24 μm, 70 μm, and 160 μm IRS (Infrared Spectrograph) - Has arrays that see in ranges within the interval 5.3 - 40 μm IRAC (Infrared Array Camera) - Has four channels at 3.6, 4.5, 5.8, and 8 μm

17. SST With Spitzer’s great sensitivity in the IR portion of the spectrum it is able to see galaxies at a redshift of z ~ 6. One of the possibilities with Spitzer is to study early galaxy formation. A study attempted to do just this for galaxies with 5.5 < z < 6.5. First IRAC identified several hundred possible high z galaxies. Then using criteria such as magnitude, image sharpness, spectroscopy, and blended objects, they were able to eliminate brown dwarfs, nearby young galaxies, and other contaminators. Now with about 100 possible galaxies, the HUDF was used to verify or eliminate any other contaminators and the final list was 13 high redshift galaxies. Now, using luminosity, bounds were put on the masses of the galaxies. From this they obtained a “representative” mass and “representative” age. The conclusion was that by z = 6 galaxies as massive as fewX1010 solar masses existed and were several hundred million years old, which is consistent with N-body simulations. Also, progenitors in these large M galaxies alone are not enough to reionize the universe.

18. SST Another study used MIPS and IRAC to look at QSOs with z > 4.5 and some with z > 6. They concluded that QSOs SED (spectral energy distribution) doesn’t differ significantly from low z (< 2) QSOs of similar luminosities. This is supported by previous observations and indicates that the emission and physical structure characterizing QSOs is established by z = 6.4, around 900 Myr after the big bang. It also indicates that QSOs of higher redshift will be difficult to identify due to dust obscuration along the sight line.

19. Compton Gamma Ray Observatory • Launched in April 1991, de-orbited and returned to Earth in June 2000 • Able to cover 6 decades of the EM spectrum from 20 keV to 30 GeV • Was the heaviest payload ever at the time (17000 kg)

20. COMPTEL OSSE Antennae EGRET Solar Panel BATSE

21. CGRO • Burst And Transient Source Experiment (BATSE) • BATSE looks in all directions for transient GRB • There are 8 detectors for BATSE • Each has NaI crystal that releases visible photons, the signal is then recorded as arrival time and gamma ray energy

22. CGRO • Oriented Scintillation Spectrometer Experiment (OSSE) • OSSE has four NaI detectors that can be independently pointed, making it possible to get a good background signal to subtract out.

23. CGRO • Energetic Gamma Ray Experiment Telescope (EGRET) • Detects the highest energy photons, up to 30 GeV • The gamma rays enter a gas filled chamber and create an electron-positron pair • The path of these is followed and the original path of the gamma ray is then known • Another NaI crystal beneath the chamber measures gamma ray energy

24. CGRO • Imaging Compton Telescope (COMPTEL) • Has two layers of gamma ray detectors • The upper layer has a liquid scintillator that scatters the photon by Compton scattering • The photon is then absorbed by the lower detector in NaI crystals • Time, energy and location are recorded in both detectors which makes it possible to determine the energy and direction of the original photon

25. EGRET!

26. EGRET • Discover of quasar 3C279 • Distance of 4 billion light years • Blazers • New class of active galaxies discovered • Emit majority of EM energy in 30 MeV – 30 GeV portion of spectrum

27. OSSE • Gamma-ray radiation from e+ and e- annihilation in interstellar medium • Radiation contained in 10 degree diameter on center of our Galaxy.

28. Galactic anticenter sky map highlights: Crab pulsar and nebula quasar PKS 0528+134 Gamma ray burst COMPTEL

29. BATSEhttp://ipac.jpl.nasa.gov/web_movies/pa/svg03-01_full.movBATSEhttp://ipac.jpl.nasa.gov/web_movies/pa/svg03-01_full.mov

30. Chandra X-Ray Observatory • Launched in July 1999 • Orbital period of 64 hours and can observe during 55 of those hours • Doesn’t take ‘pictures’, detects individual photons and records x,y,E,t of each photon • Able to detect photons with energy up to 10 keV • Chandra is in orbit around Earth and gets as high as 200 times higher than Hubble, about 1/3 the way to the moon

31. Spacecraft Module Sunshade Door Solar Panel High Resolution Camera High resolution mirror assembly CCD Imaging Spectrometer Thrusters Antennae

32. Chandra • Chandra has two sets of thrusters, one for moving (into final orbit) and one for momentum unloading (to dump momentum from gyros) • Solar arrays provide electricity to power the satellite, they convert ~2000W of electricity

33. Chandra • The sun shade door protects the internal components from the sun • With the shield, it can turn within 45 deg of the sun

34. Chandra • Low gain antenna gets all command signals and sends all telemetry data • Once every 8 hours data is sent to the deep space network, then to JPL and eventually to Operations Control Center in Cambridge, MA Low Gain Antennae

35. Chandra • HRC (High Resolution Camera) - X-rays come in and knock electrons loose. These are accelerated with a voltage and knock other electrons loose that are eventually detected. This data is then used to determine the position and energy of the X-ray

36. Chandra • ACIS (Advanced CCD Imaging Spectrometer) • Can make X-ray images and measures the energy of each incoming X-ray • Gives the capability to measure X-rays from a single chemical element

37. Chandra • High Resolution Spectrometers – HETGS and LETGS (High/Low Energy Transmission Grating Spectrometer) • LETGS is designed for .08 keV – 2keV, HETGS is designed for .4 keV – 10 keV • Gratings diffract X-rays to allow for a precise determination of their energy

38. Chandra Observations! • Valuable for study of galaxies • temp and density profiles • stellar and dark matter into discrete components • Mass-to-Light profiles flat within reff and rise outside the range

40. Chandra Observations! • Constraints on Dark Energy • Extended dark energy model: XCDM cosmolgy • Analysis of x-ray gas mass fraction and CMB set constraints: • Ωm = 0.286 • ΩX =0.75 • ωX = -1.26

41. . . .coming soon

42. James Webb Observatory