Accurate Near-Earth-Object Astrometry using Synthetic Tracking and Applications
UNKNOWN
Zhai, Chengxing↗
Engineering topics
Trahan, Russell
Publications and source records attributed to Trahan, Russell.
Performance Verification of the EXtreme PREcision Spectrograph
The EXtreme PREcision Spectrograph (EXPRES) is a new Doppler spectrograph designed to reach a radial-velocity measurement precision sufficient to detect Earth-like exoplanets orbiting nearby, bright stars. We report on extensive laboratory testing and on-sky observations to quantitatively assess the instrumental radial-velocity measurement precision of EXPRES, with a focused discussion of individual terms in the instrument error budget. We find that EXPRES can reach a single-measurement instrument calibration precision better than 10 cm s{sup −1}, not including photon noise from stellar observations. We also report on the performance of the various environmental, mechanical, and optical subsystems of EXPRES, assessing any contributions to radial-velocity error. For atmospheric and telescope related effects, this includes the fast tip-tilt guiding system, atmospheric dispersion compensation, and the chromatic exposure meter. For instrument calibration, this includes the laser fRequency comb (LFC), flat-field light source, CCD detector, and effects in the optical fibers. Modal noise is mitigated to a negligible level via a chaotic fiber agitator, which is especially important for wavelength calibration with the LFC. Regarding detector effects, we empirically assess the impact on the radial-velocity precision due to pixel-position nonuniformities and charge transfer inefficiency (CTI). EXPRES has begun its science survey to discover exoplanets orbiting G-dwarf and K-dwarf stars, in addition to transit spectroscopy and measurements of the Rossiter–McLaughlin effect.
79 ASTRONOMY AND ASTROPHYSICS↗
Synthetic Tracking on a Small Telescope
Synthetic tracking uses high speed (up to 10 Hz) low noise (<2e-) large format sensors ~16 Mpix along with a multi-vector shift/add algorithm that coadds multiple image frames to increase the signal to noise ratio (SNR) needed to detect (if present) multiple moving objects in the field of view (FOV). We published the application of synthetic tracking to look for asteroids in 2014 (Shao 2014), but recently have applied it more as well to Earth orbiting objects. We have begun testing the data processing graphical processing unit (GPU) array with a small telescope, a 28 cm Celestron RASA telescope and a low cost low noise 16 Mpix CMOS camera at a dark site in California. This system is now operational with a 2 sqdeg FOV and a limiting magnitude between ~16-17.5 stellar magnitudes (mag) depending on a number of observational parameters for short integration times. The instrument can be used to search for NEOs, where we use much longer integration times to get sensitivity ~ 20.5 mag (at new moon). Synthetic tracking provides significant improvements in both sensitivity and astrometric accuracy.
Turyshev, Slava G.↗
A Constellation of MicroSats to Search for NEOs
Large or even medium sized asteroids impacting the Earth can cause damage on a global scale. Existing and planned concepts for finding NEOs of 140 m or larger would take ~15-20 years of observation to find ~90% of them. This includes both ground and space based projects. For smaller NEOs (~50-70 m), the time scale is many decades. The reason it takes so long is because most of the NEOs have highly elliptical orbits that bring them into the inner solar system once per orbit. If they cross Earth's orbit when the Earth is on the other side of the Sun, they will not be detected. A constellation of MicroSats in orbit around the Sun can dramatically reduce the time needed to find 90% of NEOs ~100-140 m in diameter.
Trahan, Russell↗
High Precision Focal Plane Astrometry… and possibilities for the HDST
The calibration techniques we are developing for WFIRST can be also used on HDST, turning it into a revolutionary astrometric instrument. Estimated astrometric accuracy is 10’s of nano arcseconds.Two examples of what such a capability allows us to do: 1)Parallaxes of galactic neighborhood out to 100 Mpc 2) Astrometric characterization of sun like stars out to 50 p.
Shao, Mike↗