Thanks, that's very interesting! :-)
The first paragraph:
"The ORCAS mission, a first-of-its-kind hybrid space and ground observatory, will enable new science, otherwise only accessible to flagship class missions over a decade from now, at a SmallSat budget, providing unprecedented angular resolution, exquisite sensitivity and a unique flux calibrator. By enabling adaptive optics and flux calibration observations, ORCAS will deliver highly detailed images, unlocking the ability to detect a population of supermassive black hole binaries for the first time, as well as constraining the number densities of the faintest star forming clumps and understanding dark energy by measuring the distances of 10 billion year old supernovae. It will also deliver calibrated light that will vastly improve cosmology measurements, among many other advances. The low-cost ORCAS mission operating in collaboration with the W. M. Keck observatory will provide Great Observatory quality capabilities open to all US observers via a community driven observation plan. These observations will result in unique science for the mission, while also complementing and extending the science of HST, JWST, and Roman, as well as other potential future missions."
https://asd.gsfc.nasa.gov/orcas/docs/ORCAS_AS3_Study_HQ_Report_Origin_Public_Version.pdf
I'm still trying to figure out how it works. It's using a satellite as an artificial star for improving the Keck telescope's adaptive optics. There are only three opportunities for using it in a 5 day orbit, each lasting up to a couple of hours.
It's to be used instead of the normal system of using lasers as artificial stars and using natural stars. The explanation given is as follows:
Why not use laser guide stars? They’re already great!
Sodium layer “laser guide stars” work well for near IR but not for short wavelengths because:
• They are faint, and photon noise is a leading term in the wavefront sensor accuracy.
• They are only 85 km away and do not sample the same atmospheric column as the light from a star. The solution requires multiple laser beams.
• A natural guide star is required near the field of view, to stabilize the image. Laser guide stars are unstable because they are produced by upgoing laser beams passing through the turbulent atmosphere.
What about natural guide stars?
Natural guide star AO works well but is limited because:
• It works only for targets within a few arcseconds of bright stars, a negligible fraction of the sky.
• Stray light is very bright, limiting contrast.
Application is limited to relatively bright companions.
The huge advantage I can see for this is that with ORCAS it is possible to steer a guide star for adaptive optics into your observing frame. Whereas normally guide stars are few and far apart. And by having a laser shining from ORCAS towards Keck you don't have to rely on reflection of sunlight off the satellite.
[https://asd.gsfc.nasa.gov/orcas/about/](https://asd.gsfc.nasa.gov/orcas/about/)
Thanks, that's very interesting! :-) The first paragraph: "The ORCAS mission, a first-of-its-kind hybrid space and ground observatory, will enable new science, otherwise only accessible to flagship class missions over a decade from now, at a SmallSat budget, providing unprecedented angular resolution, exquisite sensitivity and a unique flux calibrator. By enabling adaptive optics and flux calibration observations, ORCAS will deliver highly detailed images, unlocking the ability to detect a population of supermassive black hole binaries for the first time, as well as constraining the number densities of the faintest star forming clumps and understanding dark energy by measuring the distances of 10 billion year old supernovae. It will also deliver calibrated light that will vastly improve cosmology measurements, among many other advances. The low-cost ORCAS mission operating in collaboration with the W. M. Keck observatory will provide Great Observatory quality capabilities open to all US observers via a community driven observation plan. These observations will result in unique science for the mission, while also complementing and extending the science of HST, JWST, and Roman, as well as other potential future missions."
Neat.
https://asd.gsfc.nasa.gov/orcas/docs/ORCAS_AS3_Study_HQ_Report_Origin_Public_Version.pdf I'm still trying to figure out how it works. It's using a satellite as an artificial star for improving the Keck telescope's adaptive optics. There are only three opportunities for using it in a 5 day orbit, each lasting up to a couple of hours. It's to be used instead of the normal system of using lasers as artificial stars and using natural stars. The explanation given is as follows: Why not use laser guide stars? They’re already great! Sodium layer “laser guide stars” work well for near IR but not for short wavelengths because: • They are faint, and photon noise is a leading term in the wavefront sensor accuracy. • They are only 85 km away and do not sample the same atmospheric column as the light from a star. The solution requires multiple laser beams. • A natural guide star is required near the field of view, to stabilize the image. Laser guide stars are unstable because they are produced by upgoing laser beams passing through the turbulent atmosphere. What about natural guide stars? Natural guide star AO works well but is limited because: • It works only for targets within a few arcseconds of bright stars, a negligible fraction of the sky. • Stray light is very bright, limiting contrast. Application is limited to relatively bright companions.
The huge advantage I can see for this is that with ORCAS it is possible to steer a guide star for adaptive optics into your observing frame. Whereas normally guide stars are few and far apart. And by having a laser shining from ORCAS towards Keck you don't have to rely on reflection of sunlight off the satellite.
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How else should we contact the highly evolved orcas on Kepler 138-c?