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C Advantages and Disadvantages of Ground- and Space-Based Options for Infrared and Visible Observations of Near Earth Objects System Advantages Disadvantages Visible/Radar SystemsâGround- and Space-Based Ground-Based Survey ï· Very good accuracy of orbit ï· Uncertainty in assessing size (e.g., PanSTARRS, CSS, ï· Obtains H (required for albedo, ~100% LSST) once size is determined) and ï· Will take decades to even some data on rotation and approach 90% completenessâ space; can give likely albedo cannot meet the George E. range, based on determination Brown, Jr. Near-Earth Object of taxonomic type and ranges of Survey Act limit associated albedos ï· Relatively low cost going forward (LSST already under construction) Ground-Based Visible ï· Visible characterization using ï· Field of view impractical for Characterization Using photometry and spectroscopy searches; effective only for Photometry and Spectroscopy gives us rotation rate, constrains characterizing known objects shape and provides taxonomy, mineralogy and surface composition Ground-Based Radar ï· Can measure accuracy of size ï· Radar field of view impractical Characterization of known objects if they pass for searches; effective only for (e.g., Goldstone, Arecibo) sufficiently close to Earth characterizing known objects ï· Can dramatically increase the accuracy of orbit after discovery by other sources ï· Best attainable size from remote observations, albedo (via size and H), rotation, shape ï· Arecibo, Goldstone already exist; maintenance costs are known. Each also has non-NEO users PREPUBLICATION COPY â SUBJECT TO FURTHER EDITORIAL CORRECTION C-1
System Advantages Disadvantages Space-Based Visisble Survey ï· Very good accuracy of orbit ï· Same uncertainty of accuracy (e.g., 0.5 m at L1 ) ï· Good characterization if multi- of size as ground-based filter or spectrometer in which ï· Many tens of years; to make case can infer albedo; measure significant contribution would light curves via imaging, need to observe near the Sun, providing rotation and tradeoff between aperture size, ultimately shape cost, and contribution beyond LSST ï· Potentially expensive at approximately $550 million plus launch ï· Options to reduce cost below Discovery missions, but will take longer to achieve completion Space-Based Visible Survey ï· Lower cost than other options ï· Insufficient sensitivity for (SmallSat platform) âapproximately $40 million assessing accuracy of size to per satellite reach George E. Brown, Jr. Near-Earth Object Survey Act criterion ï· Software for detection of orbit does not exist but under development Infrared SystemsâGround and Space Based Air-Based Characterizationâ ï· No advantages with respect to ï· Small field of view, low Aircraft Mid-Infrared (5- accuracy of size, orbit or sensitivity due to Earthâs 35 Î¼m) (e.g., SOFIA) characterization atmosphere make searches impractical Ground-Based ï· Can measure albedo given H; ï· Small field of view, low CharacterizationâMid- Size via mid-infrared sensitivity due to Earthâs Infrared (e.g., Keck, LBT, atmosphere make searches Gemini) impractical ï· Can measure rotation rate, etc., but no benefit over visible wavelength measurements SurveyâInfrared ï· Very good accuracy of size ï· Potentially expensive at $550 (50 cm at L1) ï· Feasible to characterize albedo million plus launch (via size and H) ï· Able to complete survey roughly 10 years after launch of telescope PREPUBLICATION COPY â SUBJECT TO FURTHER EDITORIAL CORRECTION C-2