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Instrument Information
IDENTIFIER urn:nasa:pds:context:instrument:tlp.lcross::1.1
NAME TOTAL LUMINANCE PHOTOMETER
TYPE PHOTOMETER
DESCRIPTION Instrument Overview =================== The Total Luminance Photometer (TLP) provides visible light intensity data of the crater flash event. The TLP instrument consists of two elements: the Sensor Electronics Module (SEM) which contains the optics and sensor assembly and signal filtering, and the Digital Electronics Module (DEM), which converts the analog sensor signal to a digital output and formats this for transmission to the DHU. The DEM is a commercial microprocessor package that was customized for LCROSS. This instrument is designed and manufactured by NASA Ames Research Center. The TLP instrument's single-element visible light detector is designed to operate at 1000 Hz to make a high fidelity record of the impact flash. The optics in the SEM delivers an unobstructed ~10 degree field-of-view. The TLP's sensor element is an uncooled Advanced Photonix, Inc. (API) avalanche photo diode (APD) packaged in a dry-air sensor container that can operate in a vacuum. The TLP SEM, located within the Payload Observation Deck (POD), is connected by an electrical harness to the TLP DEM, located at a second position on the payload panel. The DEM is interfaced with the DHU via a second cable, from which is it controlled. The SEM and DEM's peak power during operation are 2.5 and 12.0W, respectively. Scientific Objectives ===================== The total luminance photometer, operating at a 1 kHz sampling rate, provides temporal and total radiance coverage (in the visible band) of the impact flash event, expected to last a few milliseconds. At the Centaur impact, the kinetic energy of the projectile is transferred to the kinetic (ejecta) and internal energy the target (compaction, heating). A portion of the internal energy may induce vapor resulting in vibrational and rotational emission lines that will evolve with space and time. The intensity and decay of the initial flash are related to the porosity, strength, volatile content, and composition of the target. Consequently, characterization of the initial flash provides a complementary tool to understand initial energy coupling and the nature of the target. Calibration =========== The TLP has a spectral response range from 400 to 1000 nm. A conversion from DN to integrated power (in Watts), defined as an algorithm, based on laboratory test data using simulated flash spectral fluxes and colors, is summarized in the Instrument Response and Calibration Report. Ancillary data, such as the SEM sensor temperature profile, is needed to provide the necessary temperature-dependent gain corrections. This algorithm depends on the detection of the flash event above the background, As this was not detected, the algorithm was not applied to the raw data. As a result, there are no calibration files associated with this instrument. Operational Modes ================= There is a single operational mode for the total luminance photometer (TLP). The TLP is configured only to provide data for the 20 minutes prior to the Centaur impact (to provide for sufficient time for settling, which can affect data ~7-9 minutes after power on) through the flash (impact) and curtain (next 3 minutes) evolution of the experiment. The TLP is not baselined to be used during any of the other segments of the mission.
MODEL IDENTIFIER
NAIF INSTRUMENT IDENTIFIER
SERIAL NUMBER not applicable
REFERENCES unk