NASA Office of Logic Design

NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.


Mercury Laser Altimeter


Range Measurement Unit

Flight Model 1 (Block II, S/N 001)

Pre-Coat and Stake
(Left: Feb. 3, 2003
Right: Feb. 14, 2003)
Post-Stake and Coat
(Feb. 23, 2003)


Mass 117.4 grams, with conformal coat
Power 48 mA @ 5V
60 mA @ 2.5V
Functions Instrument timing, laser fire command, 6-channel time-of-flight measurement.  Two channels are multi-stop, 15 events deep.
Performance 8 Hz nominal frame rate (programmable 1, 6, 8, or 10 Hz)
Time reference: spacecraft ultrastable oscillator
Timing resolution approximately 380 ps
Design/Analysis Team Rich Katz
Igor Kleyner
Rod Barto
PCB Layout Banks Walker
Assemblers Cindy Goode, Carol Zepp, Laura Cook, Dorrie Hall, Alice Snively, Traci Lampe
Polymerics John Grondalski, Jim Cook
Quality Assurance Frances Famous, Steve Himes, Stan Kirk

A special thanks to Nick Paschalidis and Steve Jaskulek of the Johns Hopkins University/Applied Physics Laboratory for the TOF-A devices and their technical support.
tof_eval_board.jpg (81404 bytes)
TOF Evaluation/Burn-In Board
tof_eval_board_in_test.jpg (93789 bytes)
TOF Evaluation/Burn-In Board In Test
instrumentation.jpg (74353 bytes)
control_panel.jpg (69020 bytes)
Control Panel
display_sweep.jpg (60557 bytes)
Running a Time Interval Sweep, 100 ps Steps


The above article is posted courtesy of Aviation Week and Space Technology (AW&ST)
for non-commercial use.  Copyright and all publication rights remain with AW&ST.
Originally published in the July 26, 2004 edition, pages 58-59.


The above article is posted courtesy of Aviation Week and Space Technology (AW&ST)
for non-commercial use.  Copyright and all publication rights remain with AW&ST.
Originally published in the August 9, 2004 edition, pages 58-59.


For more information:

Messenger at the Kennedy Space Center, June 17, 2004

MESSENGER Mercury Laser Altimeter in Aerospace America's "2003: The Year in Review"

NASA's homepage for the planned MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission

Laser Remote Sensing Branch Page for MLA

CPU Card

Analog Card

Detector Card (EM)

Integration and Test

The repair: Activity after "shake and bake"

NASA Goddard Space Flight Center Applied Engineering & Technology Directorate

Two-Way Laser Link over Interplanetary Distance

David E. Smith,1 Maria T. Zuber,1,2 Xiaoli Sun,1 Gregory A. Neumann,1,2 John F. Cavanaugh,1 Jan F. McGarry,1 Thomas W. Zagwodzki1

1 NASA Goddard Space Flight Center

Science, January 6, 2006, page 53

Asynchronous Laser Transponder Experiment in Deep Space Using MESSENGERís Mercury Laser Altimeter

G.A. Neumann1,2, D.E. Smith1, M.T. Zuber2,1 , X. Sun1, J.F. Cavanaugh1, J.F. McGarry1, T.W. Zagwodski1

1 NASA Goddard Space Flight Center

AGU Fall Mtg. 2005

The Mercury Laser Altimeter (MLA) aboard the MErcury Surface, Space Environment, GEochemistry, and Ranging (MESSENGER) spacecraft ranged to Earth as part of its in-flight calibration activities, while NASAís Goddard Geophysical Astronomical Observatory (GGAO) fired laser pulses at MLA. On two separate afternoons, while MESSENGER was visible above the horizon at a distance of 24 million km, trains of 16 and 25 consecutive pulses were detected at GGAO with inter-arrival times matching those transmitted by MLA, while for 30 minutes on one afternoon at least 90 pulses from GGAO were detected by MLA. A linear fit to the MLA pulse time-of-flight revealed a 4.154 km/s Doppler shift in the nominal 8-Hz firing rate, with the majority of pulse centroid times fit to within 300 ps, and for the extended but weaker detections at MESSENGER, the majority could be fit by a quadratic curve within 2.5 ns. The ability to make such precise measurements, together with MESSENGER's stable on-board clock, allows a solution with formal covariances for two-way range, range-rate, and acceleration, as well as clock parameters. We discuss the implications of this calibration experiment for the measurement of orbital and geodetic parameters via asynchronous laser ranging.

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Last Revised: February 03, 2010
Web Grunt: Richard Katz