DATA_SET_DESCRIPTION |
Data Set Overview : The LRO/LCROSS spacecraft was launched on June 18, 2009, and crashed into the Cabeus crater near the Moon's south pole on October 9, 2009. The spent upper stage, called the Centaur, impacted the moon at 11:31:19.51 UTC at -84.68 deg latitude, -48.69 deg longitude, Mean Earth frame, and the LCROSS shepherding spacecraft impacted the surface at 11:35:34 UTC. This data set includes the observations made on UT October 9, 2009, of the Moon and ancillary supporting data during the LCROSS observations at the MMTO 6.5-meter telescope with the Clio imager and spectrograph. These data are the raw observations (no calibrations have been made). The Clio camera is designed for use with the MMTO 6.5-meter telescope and the f/15 adaptive secondary AO system. It incorporates an InSb 9809 ROIC 256 x 320 array of 30-micron pixels. These pixels were not binned during the LCROSS observations. The detector reads out using 4 amplifiers, providing a readout rate of 400 kHz. Readout noise is ~ 350e-. The camera has a 12 arcsecond x 16 arcsecond field of view. The camera used L' filter imaging to place the 10 arcsecond slit on the lunar surface, and a low-resolution direct vision prism with the 10 arcsecond slit to produce spectra from ~ 2.5 - 4.5 microns. Due to the optical nature of the prism, the resolving power is not linear with respect to wavelength, thus resolution will vary with wavelength. The camera is cryogenically cooled. Further descriptions of Clio can be found in Freed et al. (2004). The observations were obtained at the MMT 6.5-meter telescope on Mt. Hopkins in Arizona. The facility is owned and operated jointly by the Smithsonian Astrophysical Observatory and the University of Arizona. This is an altitude-azimuth telescope. Adaptive optics designed and developed for the MMT incorporate an adaptive secondary mirror with incoming focal ratio of f/15. During the LCROSS observations, the f/15 adaptive optics secondary was used with the MMT natural guide star top box and the Clio imager and spectrograph. Inside the top box, a beamsplitter divides the incoming light into visible and infrared components, routing light of wavelength > 1.1 micron to the Clio imager. The Clio camera was attached externally to the top box to receive the near-infrared light (higher wavelength range) signal from the beamsplitter. These observations were taken concurrently with the visible observations taken using the CCD47 camera. The visible observations taken using the CCD47 are described in the DATASET.CAT file for the data set EAR-L-MMTO_CCD47-2-EDR-LCROSS-V1.0. Observing conditions were photometric with seeing measured by wavefront sensor to be 0.38 arcseconds. The night of the LCROSS impact event was the only night we were able to take preparatory observations (other practice time allocated for observations was lost to bad weather). Processing No processing of these images has been conducted. These images are raw data; no calibrations or corrections have been made to the images. Data: The sequence of observations includes images of the Moon taken before the impact occurred using the L' filter, 2-D spectra taken covering a spectral interval of ~ 2.5 - 4.5 microns of the Cabeus crater, observations of two A0 stars (HD22859, HD43607) used for wavelength calibration (http://irtfweb.ifa.hawaii.edu/), observations of solar analogue star HD28099 (Hya 64: e.g., Farnham et al., 2000; Hardorp, 1978) for data analysis of the lunar reflectance spectra, and images of the slit on the Clio chip. For observations of standard stars, the AO system was used. About 0.33 hr prior to the LCROSS impact, the AO secondary system was triggered on a bright star near the Moon; the secondary mirror was frozen in corrected figure to remove gross aberrations caused by the atmospheric fluctuations; and the telescope was then pointed on the Cabeus crater target area. Observations covered a time range of 8 minutes before the first impact to 36 minutes after the second impact when twilight stopped observations. Spectra were taken of the Cabeus crater of the Moon where the impact was predicted to occur. The impact observations did not show any discernible effect from the impact. Quick-and-dirty spectral ratioing immediately following the event did not show any signature of the event. Based upon the observed brightness of the impact by the LCROSS shepherding satellite, we expect that we would have been able to see the event had we not had unshadowed, illuminated portions of the lunar surface in the same field of view. The observations are described in Hastie et al. (2010). Media/Format All data are stored in FITS format. References: Farnham, T. L., Schleicher, D. G., and A'Hearn, M. F. (2000). The HB narrowband comet filters: standard stars and calibrations. Icarus 147, 180 - 204. Freed, M., Hinz, P. M., Meyer, M. R., Milton, N. M., and Lloyd-Hart, M (2004). Clio: A 5 micron camera for the detection of giant exoplanets. Ground-Based Instrumentation for Astronomy, Proc. SPIE 5492, 1561 - 1571. Hardorp, J. A. (1978). The sun among the stars. I. A search for solar spectral analogs. Astron. Astrophys. 63, 383-390. Hastie, M., Bailey, V., Hinz, P., Callahan, S., Vaitheeswaran, V., Gibson, D., Porter, D. , Vilas, F. (2010). LCROSS Impact Observations from the MMT Observatory. LPSC XXXXI, #2501.
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