NASA Insignia

ORCAS Science Case: Call for White Papers

Dear Colleagues,

We are writing to solicit White Papers describing breakthrough science cases that would utilize the proposed ORCAS (Orbiting Configurable Artificial Star) adaptive optics (AO) system with an instrument package(s) for the W. M. Keck Observatory. For the first phase, we plan on a single conjugate AO system with a field of view governed by the isoplanatic patch.

Top-level Requirements are expected to be:
  1. AO Requirements
    1. Sky coverage 100% for zenith angle < 60° at Keck
    2. Observing cadence once per 3-5 days
    3. Observing time within isoplanatic patch per alignment: worst-case 1/2 hr for 0.5 µm wavelength observations at high declination, best case 4 hrs for 1.5 µm at δ = 0 (See Information and Resources, Fig A)
    4. Mission lifetime: 3-5 yrs nominal.
    5. The total number of targets is limited by the mission lifetime and total track traveled across the sky (A total accumulated track of 167 degrees, 2-4 days observation cadence, and 3-5 year mission lifetime is expected at this stage.).
  2. General Instrument Requirements
    1. Wavelength range 450 – 2500 nm (existing instruments already span 950 – 5000 nm)
    2. Diffraction limited angular resolution, FWHM = 1.22λ/D, D = 10 m
    3. Strehl ratio for instrument ≥ 0.9 with ≤ 2% variations across instrument field of view
  3. Imager Requirements
    1. Field of view radius ≥ 2.7 arcsec * (λ/0.5µm)6/5, approximate isoplanatic patch size.
    2. Pixel size ≤ λ/2D (Nyquist) at 0.5 µm = 5.2 mas (milliarcsec)
    3. Field distortion ≤ 1/100th pixel size (if used for Astrometry)
  4. Flux Calibration System
    1. Monochromatic sources covering the UV-NIR spectrum (0.25-2.0 [µm])
    2. 8-15 magnitude brightness from a distance of 200,000 km
    3. The ratio of brightness of different wavelength sources will be known to < 0.1%
    4. Beam profile uncertainty <0.3%

We seek white papers that would help define both the scientific program and the instruments to support them. Papers of any length up to 6 pages are welcome, explaining why this science is important for astronomers outside the specific area advocated.

Timeline and Key Dates:
Milestone Date
Release Call for Papers 2/11/2021
ORCAS STM Workshop
Microsoft Teams
Audio Only: +1 256-715-9946 (Conference ID: 396790828)
14:30-16:00 EDT
Final White Papers Deadline 4/5/2021
White Paper Submission:

White Papers (Drafts and Final Versions) must be submitted electronically, as a pdf document, via email to ( Files larger than 15 MB should be provided with a download link, white papers should not be longer than six pages. The Text must be single-spaced, with a minimum font size of 11 points. Templates are provided below. Participation at the ORCAS STM workshop is optional.

White Paper Structure:
  • Signature Science Case - One sentence description of the 1-2 proposed science questions.
  • Science Objectives - 1-2 paragraphs describing the specific objectives of each signature case, the scientific importance of the investigation, why it should be conducted now, and how it could support NASA goals.
  • Physical Parameters - What physical parameter is measured in each investigation?
  • Instrument Requirments (Type, wavelength range, etc.)
  • Why Orcas?
  • Proposed Science Traceability Matrix (STM).
  • Observables - A list of specific targets.

Provided is an MS-Word or LaTeX template to assist in preparing your white paper.

Final white papers will be made public on the ORCAS website, and the science cases will be used to support the NASA mission proposal.

Information and Resources:
ORCAS Information Figure