|
TECHNICAL
INFO |
Lunar
CRater Observation and Sensing Satellite (LCROSS) |
Methods of Water Ice and Water Vapor Detection
LCROSS used several independent methods for the detection of water
ice and water vapor, as well as studying the ejecta environment:
- Ice: Near-IR spectroscopy of the scattered sunlight absorption
(fundamental and overtone) features of water ice in situ
- Vapor: Near-IR spectra of H2O vapor (sublimed ice) emission
bands (overtone vibration bands at 1.4 and 1.8 um) in situ, and of
fundamental bands near 3 um from ground-based 10 m class telescopes
- Measurement of an extended OH- atmosphere via spectroscopy at the
308 nm OH- band at UV-visible wavelengths along with nearby scattering
continuum
- Spectroscopy covering the 619 nm H2O+ band and adjacent scattering
continuum
- Narrow band imaging at mid-IR wavelengths to follow thermal evolution
of plume and newly deposited regolith, which will be affected by water
vapor in the ejecta.
Table 1 LCROSS Measurements
| Product |
Measurement |
Time Scale |
Spatial Scale |
Observation “Platform” |
Water ice in plume |
1 |
sec-hrs |
0.1–10 km |
S-/SC |
Water vapor in plume |
2,3,4,5 |
sec-days |
1-100 km |
S-S/C, Ground Based, LRO |
Water ice in fresh ejecta |
6 |
min-days |
1-100 m |
S-S/C, LRO, Chandra |
Plume properties |
1,2 |
min-days |
0.1-10 km |
S-S/C, Ground Based |
Regolith properties |
6 |
days |
1-100 m |
S-S/C, LRO, Chandra |
Combining multiple independent measurement methods greatly increases
the likelihood of obtaining a constrained and definitive understanding
of the impact event and the amount of water contained in the regolith.
Furthermore, many of these measurements, because of their instrument
requirements or the timescale of the physical process, are more effectively
made either from a platform very near the event (e.g. the S-S/C) or
from ground-based telescopes. Combining measurements from the Shepherding
Spacecraft (S-S/C) with ground-based observations and (subsequent) mapping
by lunar orbiting assets (e.g., LRO and Chandrayaan-1) enhances the
overall robustness and effectiveness of the LCROSS. Table 1 lists the
various measurement techniques, the time and spatial scale best suited
to each observation, and where the measurement can be made. LRO’s
UV, IR and topographic mapping of the impact craters and associated
ejecta blankets may provide additional information about water ice and
other volatiles in the permanently shadowed regolith together with an
evaluation of the mechanical properties of lunar regolith in permanent
shadow. Similarly, a possible visit to the craters by follow-on missions
will provide detail down to the cm scale for further analysis.
Technical Information
Overview | Mission
Rationale | Spacecraft and System Description
| Instrumentation | Water Detection |
Targeting
Top
Visit the NASA Mission Site @ http://www.nasa.gov/lcross
|
