James Webb Telescope Issue - 21

Feature
Artemis I and Orion, seen below the full moon, on Launch Complex 39B of NASA's Kennedy Space Center. A launch is planned for after the release
of this issue in the next step in our return to the moon. Credit: NASA/Ben Smegelsky
Impacts of Low-Power Requirements
on the LEMS HMS Design
James Olsen, an FPGA designer at NASA's Goddard Space Flight Center
Abstract
Spacecraft designs often require optimizations for low
power. When low power is needed, design options
become limited. The Lunar Environment Monitoring Station
(LEMS) exemplifies how requirements for low power
can have ramifications across a system, even impacting
Field Programmable Gate Array (FPGA) design. LEMS
is a standalone instrument suite concept with several
that collect geophysical measurements on the moon's
surface. It has completed Technology Readiness Level
(TRL) 6 qualification. Continuous operation on the moon's
surface has many challenges, not least of which is power
management. Due to its slow rotation, lunar nighttime and
daytimes last several weeks, and many science sensors
have high power consumption. Designing a system that
can operate during hot daytime temperatures and survive
the long periods of frigid nighttime is challenging, and thus
missions attempting extended duration operations on the
moon are rare. To complete its science missions, LEMS
seeks to survive and operate on the moon for years. LEMS
utilizes a combination of techniques to solve the power
management challenge. A high-efficiency battery sustains
operations through the lunar night while LEMS alternates
between periods of being " awake " and in " hibernation. "
The subsystem of LEMS that handles this switching of
states is the Hibernation Management System (HMS).
The HMS powers on and off the more power-hungry
subsystems, such as the mass spectrometer, command
and data handling, and radio, at scheduled intervals.
The HMS is required to be very low power, which was
paramount in the design decisions made for the HMS
printed circuit board (PCB) and even in the FPGA's internal
hardware description language (HDL) code.
I. Introduction
The LEMS Lunar Environment Monitoring System (LEMS)
is a compact, autonomous, and self-sustaining instrument
package that will operate on the moon's surface. The
instruments on LEMS include a Quadrupole Mass
Spectrometer (QMS) for monitoring the lunar exosphere,
a Molecular Electronic Transducer (MET) Seismometer
capable of continuously tracking the moon's seismic
activities, a Lunar Meteoroid Monitor (LMM), and a Lunar
Electrostatic Ion Analyzer (LEIA). A diagram of LEMS
highlighting the different instruments and other components
is shown in Figure 1. An external view of LEMS is shown on
the left, and the internal layout is on the right.
LEMS was initially funded as an instrument concept by
NASA's Development of Advanced Lunar Instrumentation
Program. It has matured development at Goddard Space
HKN.ORG
21

https://hkn.ieee.org/

James Webb Telescope Issue

Table of Contents for the Digital Edition of James Webb Telescope Issue