1. Justin Albert Caltech & Univ. of Victoria Aug. 7, 2006 : A Tunable Laser in Space Dark Energy Atmospheric Physics National Security

2. Limitations on our Knowledge of Dark Energy  Calibration of redshift is a significant uncertainty in cosmological parameter measurement.  Unless we improve calibration standards to < 1%, this will be a limiting systematic for upcoming projects … : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 2

3. Understanding the Acceleration of the Universe … and others Launch date ~2013 First data ~2011 First data next year ! : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 3

4. Systematic Uncertainties are the Key  Minimizing uncertainties on these cosmological parameters is largely a matter of keeping systematic uncertainties at a minimum (especially flux as a function of redshift). From Kim, Linder, Miquel, & Mostek (MNRAS, 2004): : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 4

5. The Same Applies to Weak Gravitational Lensing  The 3 main techniques for measuring the cosmological parameters: using type Ia supernovae (“standard candles”: measure luminosity and redshift), weak gravitational lensing (shapes of galaxies “lensed” by foreground matter, as a function of their redshift), and “baryon oscillations” (ripples are present in the distribution of galaxies, as a function of redshift). All require superb redshift (spectrophotometric) calibration. From Bernstein & Jain (ApJ, 2004): : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 5

6. And Atmospheric Science Applications  The CALIPSO satellite (launched on Apr. 23 of this year) uses an Nd:YAG LIDAR laser at 1064 and 532 nm to measure the properties of clouds and the atmosphere. A tunable laser (and LIDAR receiver) could provide information in a far greater range of wavelengths. : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 6

7. Improving Fundamental Calibration Not Easy Need to get above the ATMOSPHERE Idea: Rockets (ACCESS) Another possibility: Balloons But even after you very carefully calibrate them, stars are VARIABLE (majority on the > 1% scale). Wouldn’t it be nice to just have a (man-made) source up there … ? : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 7

8. A Tunable Laser in Space 1)Would allow atmospheric calibration for all major ground- based observatories (without any worries of stellar variability). 2)A monochromatic source that covers the entire wavelength range (250 to 2500 nm) -- avoids worries about differences between stars and galaxies. 3)Would provide an always-available fundamental spectrophotometric standard source for space-based observatories (SNAP). 4)Minimizes calibration transfers; precision is limited essentially only by radiometer uncertainty (only 0.01% !!) 5)Cost could be reduced by placing on a satellite needed anyway (e.g. GPS-III [upgrade to GPS], TSAT, …). 6)Military is traditionally very interested in lasers in space… : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 8

9. Defense Applications …  Target illumination, as well as space communication. Variable wavelength (more difficult to detect / defend) : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 9

10. Straight From the Pentagon !! ---------- Forwarded message ---------- Date: Mon, 22 May 2006 13:00:52 -0400 From: Muslimov Alexander Ctr AF/A8XC To: justin@hep.caltech.edu Subject: your preprint Dr. Albert, I've just come across of your and your collaborators' preprint "Telescope Spectrophotometric and Absolute Flux Calibration..." It sounds interesting to me, and I believe you can come up with a somewhat more detailed presentation of your idea. If so, would you be interested in briefing our Directorate about your proposal at the Pentagon? Are you going to be in the DC area sometime this summer/fall? Although we don't have our own resources to fund proposals, we collaborate with the AFRL, AFOSR, DARPA and some other agencies, and could help you to find the appropriate POCs within the USAF who might be interested in your proposal. I look forward to hearing from you. Best regards, Alex Alex Muslimov, Ph.D. Staff Physicist HAF/A8XC Air Force Pentagon, Washington DC (703) 693-8476 AF/A8XC Mission: Explore, develop, advocate and link future concepts, capabilities, promising technologies and their program funding to continue transforming the Air Force into a more effective fighting force astro-ph/0604339 : : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 10

11. Tunable laser  To be purchased on Sept. 1 (UVic startup funding) Opotek Vibrant LD 355 II : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 11

12. Toward a Space-Qualified Tunable Laser …  The CALIPSO satellite uses an Nd:YAG laser from Fibertek Inc. that (clearly) is space-qualified.  Such a laser could potentially be used as a pump laser for an OPO (which would then itself need to be space-qualified).  However, it would be nice to have a laser that is closer to CW rather than pulsed, as CW would be more similar to astronomical sources (galaxies, stars, supernovae) and thus provide a better calibration.  Eli Margalith (president, Opotek Inc., Carlsbad, CA) says that he may be able to develop a very fast-pulsed (i.e. MHz frquencies) OPO system, which would be similar to (in fact indistinguishable from) a CW source.  Would need to diode-pumped (like the Fibertek laser -- due to lifetime issues, as well as input power, a flashlamp is unsuitable as an optical pump in space), durable, tested, and space qualified … : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 12

13. Several Relatively Convenenient Platforms on 2012-2016 Timescale : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 13

14. To Do: Tunable Laser and Diode Studies 1)Radiation Tests: Survivability/Degradation at 20000 km. TRIUMF irradiation facility. 2)Characterize beam divergence. Beam expander optics. 3)Explore options for eliminating moving parts (or momentum-balance when absolutely necessary), reducing cooling power. 4)Electronics / power source requirements. 5)4  -radiating source, etc. : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 14

15. Collaboration Started and Growing : A Tunable Laser in Space Caltech DOE Review 8/7/2006 : A Tunable Laser in Space J. Albert 15