The instrumentation selections and supporting observations provide multiple complementary measurement techniques and, thus, redundancy and robustness to the LCROSS mission. Moreover, multiple measurements and platforms maximize the science return.

The S-S/C payload comprises 9 instruments (Table 1): 5 cameras (1 visible, 2 Near IR, 2 Mid IR) and three spectrometers (1 visible, 2 NIR) and one photometer (Tables 2 & 3). Instrument checkout, impact rehearsal and calibration will be performed during the initial swing-by of the Moon. One hour prior to impact instruments will be powered on and will return data until impact of the S-S/C.

2. Visible Spectrometer The LCROSS S-S/C will observe the pre- and post-Centaur-impacted lunar regolith in and outside the targeted crater at a spatial resolution and viewing angle unobtainable from Earth. The visible spectrometer, developed for the LCROSS project by Ocean Optics, shall record the sunlit plume evolution, and track the evolution of OH radicals from sunlight-dissociated water vapor molecules. The visible spectrometer will measure the OH-1 (308nm) and H2O+ (619nm) transitions simultaneous which shall assess the water vapor production.

Figure 1. Fully integrated NIR spectrometer. Connection to telescope is via fiber optics.

Two identical NIR spectrometers will be coupled with fiber optics to telescopes, one focused along the impactor trajectory, the second aimed laterally through the plume towards the limb during the last ten seconds before S-S/C impact.

The NIR spectrometers utilize a no-moving-parts optical system from Polychromix. Measuring 8x6x4 cm3, consuming under 2 W, and weighing < 1 kg, each fully integrated spectrometer includes fiber optic input (NA = 0.22) and integral 2-stage TE detector cooling (ΔT > 55°C); an electronically tunable grating collects the 1.35 -2.25 micron spectrum (via Hadamard transform) each second using a singleelement InGaAs detector. Spectral resolution, specifiable in the 9 - 36 nm range, will be selected to maximize signal throughput while maintaining effective speciation. Developed for industrial process monitoring and control, this NIR spectrometer exemplifies leverage of rugged COTS instrumentation. (See Figure 1)

4. Mid IR Cameras Pre- and post- impact thermal images of the impact terrain will be obtained from Mid-IR cameras on the S-S/C to characterize the surface material (rock vs. regolith), obtain the thermal evolution of the plume (which is dependent on the water content), and observe the ejecta blanket and freshly exposed regolith. The baseline mid-IR sensors will be a flight-proven Alphasilicon uncooled micro-bolometer most sensitive in the 7-14 micron spectral range, outputting in PAL format (384H x 288V pixels).

5. Total Luminescent Photometer (TLP) A total visible luminance photometer will be used to observe a possible impact flash. The light flash is due to thermal heating and vaporization or the impactor and surface material. The shape of the light curve can be used to bound certain initial conditions of the impact, and the flash peak intensity depends on the angle of impact, target, and projectile types.

6. Data Handling Unit A Digital Handling Unit (DHU) accommodates all sensor interfaces, all digital video system functionality and all interfaces with the S-S/C avionics. Both the visible and MIR cameras and the DHU are flight proven having flown on both launch systems (MRT KASP ABM tests) and spacecraft (GD Spectrum Astro).

Technical Information
Overview | Mission Rationale | Spacecraft and System Description | Instrumentation | Water Detection | Targeting
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