The Mars Microphone
LIDAR and Microphone Team
The LIDAR was designed in a bistatic scheme with a separate transmitter and two receiver channels. It consists of three assemblies:
The total mass of the instrument is only 940 grams (about 2 pounds) and a total volume is 950 cubic centimeters in both assemblies. The power consumption provides a maximum of 4 Watts during 10-minute measurements.
- A sensor assembly,
- An electronic assembly, and
- The interconnecting cables.
Engineers designed the LIDAR to operate in the temperature range from -100 to 50 degrees Celsius (-148 to 122 degrees Fahrenheit) under lower pressure, near one millibar. It is connected to the board by an RS-422 interface and generates science data up to 25.6 Kb per day for standard operation scenario, which is a limit from the spacecraft.
The LIDAR also has a high pressure variometer for studying correlation of optical atmospheric characteristics with very low frequency sounds (infrasounds) and changing pressure.
The laser transmitter is a galium-aluminum-arsenic pulse laser diode emitting one microJoule in 20-nanosecond long pulses at 890-nanometer wavelength. The laser beam has a linear polarization and a 2-milliradian divergence with the output 54x34 mm2 clear aperture. The laser operates with repetition rate of about 20 to 25 kHz.
Outside daylight background irradiance is the main source of noise inside the one mrad field-of-view of the receiver channel. The background irradiance is reduced by an optical interference filter having a bandwidth of 10 nm (FWHM) at 890 nm with 50 percent transmission and 15-millimeter clear aperture only. One of the receiver channels has polarizer. Its axes are coincident with the LIDAR beam polarization.
Full sounding distance is 750 meters (2,461 feet) with 5 meters resolution along the trace or the 32-second total integrating time. The single cycle has a 10-minute duration and consists of three active measurements by each channel simultaneously and 12 passive measurements of sky brightness.
for Mars Polar Lander"
By V.M.Linkin, A.N.Lipatov, V.S.Makarov, L.I.Kchlioustova, S.M.Pershin, A.N.Lyash,
A.V.Buckharin A.V.Tiurin, G.P.Arumov, B.S.Zubkov, E.N.Evlanov.