NASA Insignia


ORCAS would provide science that would help us answer some of the great mysteries including the existence and growth of supermassive black holes through the merger of protogalaxies and the accretion of gas and stars, and cosmic dark energy. ORCAS observations would allow us to detect intermediate and supermassive black holes, measure the dark energy equation of state, reduce errors and increase accuracy in the measurement of Supernovae, and constrain the number densities of the faintest Star Forming clumps, among other science drivers. ORCAS is principally driven by the science goals above, which will be enabled through observations of AGN, the supernova cosmic distance scale, and high redshift galaxies. Observations of flux calibration, exoplanets, and the Solar System will also be enabled by ORCAS.

A single ORCAS spacecraft will provide around 300 AO mode observations and 1,500 Flux Calibration mode observations.

We aim to propose a budget of less than $75 M (30 percent of which is contingency) to NASA for construction of the spacecraft bus, ground elements, payloads, and operations. The spacecraft and payload costs is estimated at around $40 M.

Yes; ORCAS is required to provide <2" pointing accuracy, where the laser system can provide ~0.2" pointing accuracy, a margin of x10. The spacecraft first points the laser payload field of view to the target, followed by the laser payload optical guidance system providing the fine tuning within the field of view.

Yes; ORCAS can enable simultaneous scientific investigations with multiple instruments, spanning the entire observable wavelengths in a single observation. In fact, any telescope on the summit that chooses to use ORCAS can do so as long as they are integrated to the observation program.

ORCAS will be able to use current and developed Keck instruments and will have a wavelength coverage around 0.5 - 5 microns. ORCAS will provide two calibration wavelengths to support both visible and near infrared observations.

ORCAS is required to operate for three years, yet its design implies it could operate longer than that (~ 5 years), where the mission is ultimately limited by fuel usage for target selection. ORCAS could launch four and a half years after selection.

Ideally, ORCAS will ride share to a high elliptical orbit with apogee near the desired direction. However, ORCAS propulsion system and mission operation concept were developed to additionally support GTO or Artemis ride share options.

ORCAS can stay passively within the isoplanatic patch for up to a few hours depending on target star declination and the observable wavelength.

The spacecraft will have 112 kg of Xenon propellant. This corresponds to 18 kg of fuel for the initial maneuvers to the science orbit and 54 kg allocated for maneuvers between observation orbits. This is enough fuel for 300 AO observations during the mission lifetime.

Sodium layer "laser guide stars" work well for near IR but not for short wavelengths because:

  • Sodium layer stars are faint, and photon noise is a leading term in the wavefront sensor accuracy. The required brightness scales as λ-6. As wavelength decreases, the number of atmospheric turbulence cells increases, their size decreases, the speed of measurement increases, and the measurement accuracy requirement increases.
  • Sodium layer guide stars 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, multiple wavefront sensors, and complex tomography algorithms. Accuracy is limited.
  • A natural guide star is required near the field of view, to stabilize the image. The sodium layer guide stars are unstable because they are produced by upgoing laser beams passing through the turbulent atmosphere. Some regions are unobservable.

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 to about 103 or 104 without a coronagraph. Application is limited to relatively bright companions.
  • Extreme AO achieves higher contrast of 105 with reduced efficiency.