NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) has completed
the commissioning phase, and now is ready to begin the mission’s primary science
phase. After the successful Orbit Lowering Maneuver (OLM-3) on Nov. 10, LADEE
was in an elliptic pre-science orbit. The first six days in this orbit were
dedicated to completing the science instrument commissioning, doing
opportunistic science measurements in coordination with NASA’s Lunar
Reconnaissance Orbiter (LRO) spacecraft, and taking measurements of the impact
of the Leonids meteor shower on the lunar environment.
The team was able to conduct preliminary science activities when LADEE’s
orbit brought it closest to the surface of the moon and across the sunrise
terminator – the transition from night to day. After those science activities
LADEE completed the fourth and final block of Lunar Laser Communication
Demonstration (LLCD) operations in the commissioning phase.
Everything has been going very well during commissioning activities, even
though we sometimes had to deal with unexpected events. For example, on Nov. 19,
at the end of an LLCD downlink of spacecraft main memory, LADEE experienced an
unexpected processor reboot and came back up in safe mode. A safe mode is a
self-protective measure that the spacecraft takes when something unexpected
occurs. After re-establishing communications and looking at the data leading up
to the event, the engineering team determined that the reboot was triggered by a
watchdog timer. These timers are designed to detect when the spacecraft
processor stops responding, indicating that something unusual has happened. This
could occur for a wide variety of reasons, from a radiation event to a
high-priority software overloading LADEE’s onboard computer processor.
Engineers were able to determine the event data was clean leading up to the
reboot, so after initial analysis the team decided to bring the spacecraft out
of safe mode and continue the LLCD experiments. The spacecraft and LLCD have
performed normally since that point.
Once the LLCD experiment phase was completed, the team prepared for and
performed the OLM-4 maneuver at 8:53 p.m. PST Nov. 20. This main engine burn
lowered the spacecraft into the final science orbit, which varies between 20 and
60 Km above the lunar surface. The varying altitude is caused by the moon’s
uneven gravity field. This was the final planned use of the large main engine on
the LADEE spacecraft, which has served us extremely well during the mission.
The mission now is ready to perform the main science measurements over the next
several months.
Butler Hine
Ames Research Center, Moffett Field, Calif.
Image Credit: NASA/Ames
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NASA Spacecraft Begins Collecting Lunar Atmosphere Data
NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) is ready to
begin collecting science data about the moon.
On Nov. 20, the spacecraft successfully entered its planned orbit around the
moon's equator -- a unique position allowing the small probe to make frequent
passes from lunar day to lunar night. This will provide a full scope of the
changes and processes occurring within the moon's tenuous atmosphere.
LADEE now orbits the moon about every two hours at an altitude of eight to 37
miles (12-60 kilometers) above the moon's surface. For about 100 days, the
spacecraft will gather detailed information about the structure and composition
of the thin lunar atmosphere and determine whether dust is being lofted into the
lunar sky.
"A thorough understanding of the characteristics of our lunar neighbor will
help researchers understand other small bodies in the solar system, such as
asteroids, Mercury, and the moons of outer planets," said Sarah Noble, LADEE
program scientist at NASA Headquarters in Washington.
Scientists also will be able to study the conditions in the atmosphere during
lunar sunrise and sunset, where previous crewed and robotic missions detected a
mysterious glow of rays and streamers reaching high into the lunar sky.
On Nov. 20, flight controllers in the LADEE Mission Operations Center at
NASA's Ames Research Center in Moffett Field, Calif., confirmed LADEE performed
a crucial burn of its orbit control system to lower the spacecraft into its
optimal position to enable science collection. Mission managers will
continuously monitor the spacecraft's altitude and make adjustments as
necessary.
"Due to the lumpiness of the moon's gravitational field, LADEE's orbit
requires significant maintenance activity with maneuvers taking place as often
as every three to five days, or as infrequently as once every two weeks," said
Butler Hine, LADEE project manager at Ames. "LADEE will perform regular orbital
maintenance maneuvers to keep the spacecraft’s altitude within a safe range
above the surface that maximizes the science return."
In addition to science instruments, the spacecraft carried the Lunar Laser
Communications Demonstration, NASA's first high-data-rate laser communication
system. It is designed to enable satellite communication at rates similar to
those of high-speed fiber optic networks on Earth. The system was tested
successfully during the commissioning phase of the mission, while LADEE was
still at a higher altitude.
LADEE was launched Sept. 6 on a U.S. Air Force Minotaur V, an excess
ballistic missile converted into a space launch vehicle and operated by Orbital
Sciences Corp. of Dulles, Va. LADEE is the first spacecraft designed, developed,
built, integrated and tested at Ames. It also was the first probe launched
beyond Earth orbit from NASA's Wallops Flight Facility on the Virginia
coast.
NASA's Science Mission Directorate in Washington funds the LADEE mission.
Ames manages the overall mission and serves as a base for mission operations and
real-time control of the probe. NASA's Goddard Space Flight Center in Greenbelt,
Md., manages the science instruments and technology demonstration payload, the
science operations center and overall mission support. NASA's Marshall Space
Flight Center in Huntsville, Ala., manages LADEE within the Lunar Quest Program
Office.
For more information about the LADEE mission, visit:
NASA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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