The “Great Observatories” ( The Engineering Side)

1. The “Great Observatories”(The Engineering Side) Randy Moore RE-SEED Volunteer http://www.bostonreseedcenter.org/ Mechanical Engineer (Ret)

2. Electromagnetic Spectrum

3. Why Telescopes in Space??? Image of Altair as seen from a ground based telescope distorted by the layers of atmosphere Same star as seen from a space based telescope

4. Refraction The Earth’s Atmosphere acts very much like a prism or bent window BUT.. The atmosphere is not stationary.. So, the distortions move like waves on a pond

5. The Primary Space Telescopes

6. HUBBLE and THE BIG BANG Edwin Hubble is noted as the “father” of the “Big Bang Theory” though it was first conceived years before. Observations from the Hubble telescope and other observatories have made astounding discoveries which support the theory.

7. Hubble in Flight Launch date — 24 April 1990 - Orbital Period 96 minutes

9. HYPERBOLIC SECONDARY MIRROR PARABOLICPRIMARYMIRROR

10. Off Axis Cassegrain Telescope Configuration A design considered for Spitzer

11. The Mathematics of Telescopes Cartesian equation: y = ax2 + bx + c

12. Spitzer Infrared Space Telescope launched on August 25, 2003 – Orbital Period 1 year (helicentric) Within about a week of May 12, 2009 the telescope was expected to run out of the liquid helium needed to chill some of its instruments to operating temperatures. This would end its primary mission

13. Compton Gamma Ray Observatory Launched in 1991 – Orbital Period 90 minutes (deorbited in June of 2000) deployed in low earth orbit at 450 km (280 miles) to avoid the Van Allen Radiation Belts

14. The Chandra X-Ray Astrophysics Facility Launched from, Kennedy Space Center 23 July 1999. Orbital Period 65 hours http://chandra.harvard.edu/

15. Chandra in the Shuttle Bay just before its deployment with the robot arm Chandra and the upper stage booster deployed from the Shuttle and ready for orbit insertion

16. Chandra’s Wolter Mirrors “Grazing incidence” imagery for X-Rays with nested cylindrical mirrors Imaging x-rays is a lot like skipping stone on a pond..

17. A schematic side view of Chandra's orbit, showing the inner and outer radiation belts This elliptical orbit 10,000 km perigee, 100,000 km apogee, yields 55hr observing time per orbit

18. Design considerations for a space based telescope Launch (extreme random vibration, acoustic loads & g-loads) Thermal Unbalanced moments (stability) Newton Lives! F=Ma Kinematic mountings Weight (and to lesser extent, volume) $10,000 per lb to launch!!!! Periodic calibration & telemetry Effects of “out gassing” Lubrication of mechanisms Effects of monatomic gasses Radiation effects =materials and single event upsets in electronics SpaceCraft ‘Charging” Micrometeriorites & small “junk” Redundancy Most mechanical designs are stress based.. telescopes are deflection based

19. Design considerations for a space based telescope Part 2 • What do I do with it at mission’s end?? • Allow it to “de-orbit” and fall to earth • Design it for “burn up” on re-entry • Design in an engine to send it off into deep space • Design it to be serviced / re-fitted May the “M x a” be with you

20. Space JunkDebris Plot by NASA The graphics are computer generated images of objects in Earth orbit that are currently being tracked. Approximately 95% of the objects in this illustration are orbital debris, i.e., not functional satellites

21. Random Vibration Testing The “land of broken dreams”

22. Typical Momentum wheel for Space Craft Attitude Control One for Each Axis to be Controlled These would also have to compensate for “unbalanced” forces from the focal plane instruments

23. Detector Vacuum Housing Shows the Titanium Housing with a “50%” lightweighting

24. The Hubble primary mirror in the clean room waiting for assembly into the telescope structure

25. HRC’s Microchannel Plate Based Detector Cesium Iodide coating Grid of fine gold wires

26. Schematic view of the HRC

27. Chandra’s Picture of Cassiopeia

29. Why are these images actually looking back in time?? The objects that are being looked at are so far away that the light took may years to get here - so long, in fact that the object may even no longer exist, or exist in a different state of evolution by the time we “see” it!!

30. The Nature of Light AN OBSERVOR TRAVELS MUCH LIKE RIPPLES ON A POND

31. How do astronomers measure the distance to stars? Is it accurate? • In order to calculate how far away a star is, astronomers use a method called parallax. During Earth's orbit, near stars seem to shift their position against the farther stars. This is called parallax shift. By observing the distance of the shift and knowing the diameter of the Earth's orbit, astronomers are able to calculate the parallax angle across the sky. • If you follow the line on the diagram from the Earth in January to the appearance of the star in January, then the line from the Earth in July to the appearance of the star in July, you will see that they intersect in the middle. This is the true location of the star. The distance of the star can then be measured using trigonometry. • The smaller the parallax shift, the farther away from earth the star is. This method is only accurate for stars within a few hundred light-years of Earth, since when the stars are very far away, the parallax shift is too small to measure. • The method of measuring distance to stars beyond 100 light-years is to use Cepheid variable stars. These stars change in brightness over time, with a regular period. This period is directly related to the luminosity of the star--brighter stars have a longer period of light variation. Comparing the apparent brightness of the star to the true brightness allows the astronomer to calculate the distance to the star. This method was discovered by American astronomer Henrietta Leavitt in 1912 and used in the early part of the century to find distances to many globular clusters.

32. The NASA-led Swift mission has measured the distance to two gamma-ray bursts -- back to back, from opposite parts of the sky -- and both were from over nine billion light years away, unleashed billions of years before the Sun and Earth formed. These represent the mission's first direct distance, or redshift, measurements, its latest milestone since being launched in November 2004. The distances were attained with Swift's Ultraviolet/OpticalTelescope (UVOT).

33. Large Advanced Mirror Program (LAMP) To demonstrate the ability to fabricate the large mirror required by an SBL, the Large Advanced Mirror Program (LAMP) built a lightweight, segmented 4 m diameter mirror on which testing was completed in 1989 This program and its predecessor (HALO) also served as “proof of concept” for large active segmented mirrors for both space based & ground based telescope applications

34. Future telescopes (James Webb) will use segmented, lightweighted mirrors based in part on the technologies developed on HALO & LAMP and used on the Keck projects

35. Active segmented mirror including a plurality of piezoelectric drivers (atmospheric compensation) See also: Advanced Technology Large-Aperture Space Telescope (ATLAST)

36. The Kepler Telescope A Search for Habitable Planets http://kepler.nasa.gov/

37. The Galaxy Evolution Explorer (GALEX) is an orbiting space telescope observing galaxies in ultraviolet light across 10 billion years of cosmic history. A Pegasus rocket launched GALEX into orbit at 8 a.m. EDT on April 28th, 2003. Led by the California Institute of Technology, GALEX is conducting several first-of-a-kind sky surveys, including an extra-galactic (beyond our galaxy) ultraviolet all-sky survey

38. Other Optical System Projects Atmospheric Compensation System for AMOS (Maui) Viking 1976 (First photos on the surface of another planet) “Corona” Reconnaissance Satellite (Photos of Cuban Missile Silos) U-2 Seyers Airborne Photos ALOT Telescope & Zenith Star Part of Anti-Ballistic Defense The Keck Telescopes