Justin Albert Caltech & Univ. of Victoria Aug. 7, 2006

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Justin AlbertCaltech & Univ. of Victoria

Aug. 7, 2006

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::A Tunable Laser A Tunable Laser

in Spacein Space

Dark EnergyDark EnergyAtmospheric Atmospheric

PhysicsPhysics

National National SecuritySecurity

Limitations on our Knowledge of Dark EnergyLimitations 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 …

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Caltech DOE Review 8/7/2006 : A Tunable Laser in Space : A Tunable Laser in Space J. Albert 2QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

Understanding the Acceleration of the UniverseUnderstanding the Acceleration of the Universe





… and othersLaunch date ~2013 First data ~2011

First data next year !


Systematic Uncertainties are the KeySystematic 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):


The Same Applies to Weak Gravitational LensingThe 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):


And Atmospheric Science ApplicationsAnd 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.




Improving Fundamental CalibrationImproving Fundamental Calibration



Not EasyNeed 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 SpaceA 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…


Defense ApplicationsDefense Applications … …

Target illumination, as well as space communication.

Variable wavelength (more difficult to detect / defend)


Straight From the Pentagon !!Straight From the Pentagon !!---------- Forwarded message ----------Date: Mon, 22 May 2006 13:00:52 -0400From: Muslimov Alexander Ctr AF/A8XC <[email protected]>To: [email protected]: your preprint

Dr. Albert,

I've just come across of your and your collaborators' preprint "TelescopeSpectrophotometric and Absolute Flux Calibration ..."

It sounds interesting to me, and I believe you can come up with a somewhatmore detailed presentation of your idea. If so, would you be interestedin briefing our Directorate about your proposal at the Pentagon? Are yougoing to be in the DC area sometime this summer/fall? Although we don'thave our own resources to fund proposals, we collaborate with the AFRL,AFOSR, DARPA and some other agencies, and could help you to find theappropriate 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) 693-8476AF/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 :


Tunable laserTunable laser

To be purchased on Sept. 1 (UVic startup funding)

Opotek Vibrant LD 355 II

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Toward a Space-Qualified Tunable Laser …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 …




Several Relatively Convenenient Platforms Several Relatively Convenenient Platforms on 2012-2016 Timescaleon 2012-2016 Timescale










To DoTo Do: Tunable Laser and Diode Studies: 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.


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Collaboration Started and GrowingCollaboration Started and Growing

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

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Justin Albert Caltech & Univ. of Victoria Aug. 7, 2006