AEROSPACE INDUSTRY
UPDATE
November/December
2017
McIlvaine Company
TABLE OF CONTENTS
Tiny Monitoring Satellite Built in MIT Cleanroom
NASA Builds its Next Mars Rover Mission
In just a few years, NASA's next Mars rover mission will be flying to the Red
Planet.
At a glance, it looks a lot like its predecessor, the Curiosity Mars rover. But
there's no doubt it's a souped-up science machine: It has seven new instruments,
redesigned wheels and more autonomy. A drill will capture rock cores, while a
caching system with a miniature robotic arm will seal up these samples. Then,
they'll be deposited on the Martian surface for possible pickup by a future
mission.
This new hardware is being developed at NASA's Jet Propulsion Laboratory,
Pasadena, California, which manages the mission for the agency. It includes the
Mars 2020 mission's cruise stage, which will fly the rover through space, and
the descent stage, a rocket-powered "sky crane" that will lower it to the
planet's surface. Both of these stages have recently moved into JPL's Spacecraft
Assembly Facility.
Mars 2020 relies heavily on the system designs and spare hardware previously
created for Mars Science Laboratory's Curiosity rover, which landed in 2012.
Roughly 85 percent of the new rover's mass is based on this "heritage hardware."
"The fact that so much of the hardware has already been designed -- or even
already exists -- is a major advantage for this mission," said Jim Watzin,
director of NASA's Mars Exploration Program. "It saves us money, time and most
of all, reduces risk."
Despite its similarities to Mars Science Laboratory, the new mission has very
different goals. Mars 2020's instruments will seek signs of ancient life by
studying terrain that is now inhospitable, but once held flowing rivers and
lakes, more than 3.5 billion years ago.
To achieve these new goals, the rover has a suite of cutting-edge science
instruments. It will seek out biosignatures on a microbial scale: An X-ray
spectrometer will target spots as small as a grain of table salt, while an
ultraviolet laser will detect the "glow" from excited rings of carbon atoms. A
ground-penetrating radar will be the first instrument to look under the surface
of Mars, mapping layers of rock, water and ice up to 30 feet (10 meters) deep,
depending on the material.
The rover is getting some upgraded Curiosity hardware, including color cameras,
a zoom lens and a laser that can vaporize rocks and soil to analyze their
chemistry.
"Our next instruments will build on the success of MSL, which was a proving
ground for new technology," said George Tahu, NASA's Mars 2020 program
executive. "These will gather science data in ways that weren't possible
before."
The mission will also undertake a marathon sample hunt: The rover team will try
to drill at least 20 rock cores, and possibly as many as 30 or 40, for possible
future return to Earth.
"Whether life ever existed beyond Earth is one of the grand questions humans
seek to answer," said Ken Farley of JPL, Mars 2020's project scientist. "What we
learn from the samples collected during this mission has the potential to
address whether we're alone in the universe."
JPL is also developing a crucial new landing technology called terrain-relative
navigation. As the descent stage approaches the Martian surface, it will use
computer vision to compare the landscape with pre-loaded terrain maps. This
technology will guide the descent stage to safe landing sites, correcting its
course along the way.
A related technology called the range trigger will use location and velocity to
determine when to fire the spacecraft's parachute. That change will narrow the
landing ellipse by more than 50 percent.
"Terrain-relative navigation enables us to go to sites that were ruled too risky
for Curiosity to explore," said Al Chen of JPL, the Mars 2020 entry, descent and
landing lead. "The range trigger lets us land closer to areas of scientific
interest, shaving miles -- potentially as much as a year -- off a rover's
journey."
This approach to minimizing landing errors will be critical in guiding any
future mission dedicated to retrieving the Mars 2020 samples, Chen said.
Site selection has been another milestone for the mission. In February, the
science community narrowed the list of potential landing sites from eight to
three. Those three remaining sites represent fundamentally different
environments that could have harbored primitive life: an ancient lakebed called
Jezero Crater; Northeast Syrtis, where warm waters may have chemically
interacted with subsurface rocks; and a possible hot springs at Columbia Hills.
All three sites have rich geology and may potentially harbor signs of past
microbial life. A final landing site decision is still more than a year away.
"In the coming years, the 2020 science team will be weighing the advantages and
disadvantages of each of these sites," Farley said. "It is by far the most
important decision we have ahead of us."
Tiny Monitoring Satellite Built in MIT Cleanroom
In the darkness of 2 a.m. on Aug. 26, the sky over Cape Canaveral, Fla., lit up
with the bright plume of a Minotaur rocket lifting off from its launch pad.
Aboard the rocket, a satellite developed by the MIT Lincoln Laboratory for the
U.S. Air Force's Operationally Responsive Space (ORS) Office awaited its
deployment into low Earth orbit.
The ORS-5 SensorSat spacecraft is on a 3-year mission to continually scan the
geosynchronous belt, which at about 36,000 kilometers above Earth is home to a
great number of satellites indispensable to the national economy and security.
Data collected by SensorSat will help the United States keep a protective eye on
the movements of satellites and space debris in the belt.
"There was nothing like seeing the massive Minotaur IV blast our creation into
orbit, and then getting those familiar telemetry messages to indicate that it's
really up there and operating just as it did in thermal vacuum testing," says
Andrew Stimac, the SensorSat program manager and assistant leader of the Lincoln
Laboratory's Integrated Systems and Concepts Group.
In the months that SensorSat has been in orbit, it has undergone a complete
checkout process, opened the cover of its optical system, and collected the
first imagery of objects in the geosynchronous belt. The quality of the initial
images has demonstrated that SensorSat utilizes a highly capable optical system
that is able to conduct its required mission.
The 226-pound SensorSat is small in comparison to current U.S. satellites that
monitor activity in the geosynchronous belt. SensorSat's size and its optical
system design, which uses a smaller aperture, make it a lower-cost, faster-built
option for space surveillance missions than the large systems designed for
missions of 10 years or more.
"SensorSat is essentially a simple design, but it is a highly sensitive
instrument that is one-tenth the size and one-tenth the cost of today's large
satellites," says Grant Stokes, head of the Lincoln Laboratory's Space Systems
and Technology Division, which collaborated with the Engineering Division to
develop and build the satellite.
Traditional large surveillance satellites are designed to collect data on
objects known to be in the geosynchronous belt. The optical systems on those
satellites are mounted on gimbals so that they can turn their focus toward the
targeted objects. SensorSat works on a different concept: Its fixed optical
system surveys each portion of the belt that is within its current field of view
as the satellite orbits Earth.
SensorSat makes approximately 14 passes around Earth each day, providing
up-to-date views of activity in the geosynchronous belt. Stokes compared
SensorSat's surveillance process to that of airport radars that continuously
rotate to visualize a local airspace. Because SensorSat is not aimed at specific
known objects, a secondary benefit to its concept of operations is that it may
see new objects that pose threats to satellites within the belt.
The adoption of SensorSat-like systems that can be cost-effectively built on
short timelines could also make it practical for the United States to more
frequently deploy new satellites to keep pace with evolving technology.
SensorSat development and testing were accomplished in just three years, a
period about one-third of that needed to develop and field large surveillance
satellites. The SensorSat engineering effort involved the design, fabrication,
and testing of the satellite structure and cover mechanism, lens optomechanics,
telescope baffle, charge-coupled device packaging, electrical cabling, and
thermal control.
The assembly, integration, and testing were conducted in Lincoln Laboratory's
cleanroom facilities and its Engineering Test Laboratory. According to Mark
Bury, assistant leader of the Laboratory's Structural and Thermal-Fluids
Engineering Group, the shock, vibration, attitude control system, and
thermal-vacuum testing performed were critical in validating SensorSat against
the expected launch and space conditions it would need to endure.
"Perhaps the most important events occurred during thermal-vacuum testing," Bury
says. "The satellite is exposed to conditions similar to those on orbit, and we
used that test to validate our thermal design. Even more important, the
thermal-vacuum test enabled us to get significant runtime on the avionics and
components within the spacecraft, emulating the communication cadence and data
streams that we would eventually see on orbit."
On July 7, less than two months before launch, SensorSat was shipped to Florida
for installation on Orbital ATK's Minotaur IV inside a large cleanroom facility
at Astrotech Space Operations, located just outside the Kennedy Space Center. A
team from the Lincoln Laboratory performed final assembly steps and prepared the
satellite with the software uploads needed initially on orbit.
Joint operations were then conducted with Orbital ATK to complete the mechanical
and electrical integration prior to encapsulation with the rocket fairing. The
integrated assembly was then transported from Astrotech to the Cape Canaveral
Air Force Station launch pad 46 in mid-August.
SensorSat, which resides directly above the equator, orbits at an inclination of
zero degrees, an orientation that Stokes says required very precise deployment
of the satellite. The Minotaur IV, modified from a 25-year-old Air Force rocket
design and now operated by Orbital ATK, was up to the challenge, using two new
rocket motors to provide the extra lift needed to reach the equatorial orbit.
SensorSat is now orbiting Earth and collecting data to fulfill its space
surveillance mission.
Source: MIT
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