| 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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