Lunar Atmosphere and Dust Environment Explorer

Lunar Atmosphere and Dust Environment Explorer

Artist's depiction of LADEE in lunar orbit
Mission type Lunar atmospheric research
Operator NASA
COSPAR ID 2013-047A
SATCAT № 39246
Website nasa.gov/mission_pages/ladee/main/
Mission duration Primary mission: 100 days
Extended mission: 28 days
Total duration: 223 days
Spacecraft properties
Bus MCSB
Manufacturer Ames Research Center
Launch mass 383 kg (844 lb)[1]
Dry mass 248.2 kg (547 lb)[1]
Payload mass 49.6 kg (109 lb)[1]
Dimensions 1.85×1.85×2.37 m (6.1×6.1×7.8 ft)[1]
Power 295 watts[1]
Start of mission
Launch date September 7, 2013, 03:27 (2013-09-07UTC03:27Z) UTC[2]
Rocket Minotaur V Flight 1
Launch site MARS LP-0B
Contractor Orbital Sciences Corporation[1]
End of mission
Disposal Deorbited
Decay date April 18, 2014 (2014-04-19), ~04:30 UTC
Orbital parameters
Reference system Selenocentric[3]
Periselene 25–50 km (16–31 mi)[4]
Aposelene 60–80 km (37–50 mi)[4]
Inclination 157 degrees[4]
Period 111.5 to 116.5 minutes[1]
Epoch Planned (science phase)
Moon orbiter
Orbital insertion October 6, 2013, 10:57 UTC

The Lunar Atmosphere and Dust Environment Explorer (LADEE, pronounced /ˈlæd.iː/[5]) was a NASA lunar exploration and technology demonstration mission. It was launched on a Minotaur V rocket from the Mid-Atlantic Regional Spaceport on September 7, 2013.[6] During its seven-month mission, LADEE orbited around the Moon's equator, using its instruments to study the lunar exosphere and dust in the Moon's vicinity. Instruments included a dust detector, neutral mass spectrometer, and ultraviolet-visible spectrometer, as well as a technology demonstration consisting of a laser communications terminal.[7] The mission ended on April 18, 2014, when the spacecraft's controllers intentionally crashed LADEE into the far side of the Moon,[8][9] which, later, was determined to be near the eastern rim of Sundman V crater.[10]

Planning and preparations

LADEE was announced during the presentation of NASA's FY09 budget in February 2008. It was initially planned to be launched with the Gravity Recovery and Interior Laboratory (GRAIL) satellites.[11]

Mechanical tests including acoustic, vibration and shock tests were completed prior to full-scale thermal vacuum chamber testing at NASA's Ames Research Center in April 2013.[12] During August 2013, LADEE underwent final balancing, fuelling and mounting on the launcher, and all pre-launch activities were complete by August 31, ready for the launch window which opened on September 6.[13]

NASA Ames was responsible for the day-to-day functions of LADEE while the Goddard Space Flight Center operated the sensor suite and technology demonstration payloads as well as managing launch operations.[14] The LADEE mission cost approximately $280 million, which included spacecraft development and science instruments, launch services, mission operations, science processing and relay support.[1]

Atmospheric glow

At sunrise and sunset various Apollo crews saw glows and rays.[15] This Apollo 17 sketch depicts the mysterious twilight rays.

The Moon may have a tenuous atmosphere of moving particles constantly leaping up from and falling back to the Moon's surface, giving rise to a "dust atmosphere" that looks static but is composed of dust particles in constant motion. According to models proposed starting from 1956,[16] on the daylit side of the Moon, solar ultraviolet and X-ray radiation is energetic enough to knock electrons out of atoms and molecules in the lunar soil. Positive charges build up until the tiniest particles of lunar dust (measuring 1 micrometre and smaller) are repelled from the surface and lofted anywhere from metres to kilometres high, with the smallest particles reaching the highest altitudes.[16][17][18][19] Eventually they fall back toward the surface where the process is repeated. On the night side, the dust is negatively charged by electrons in the solar wind. Indeed, the "fountain model" suggests that the night side would charge up to higher voltages than the day side, possibly launching dust particles to higher velocities and altitudes.[17] This effect could be further enhanced during the portion of the Moon's orbit where it passes through Earth's magnetotail;[20] see Magnetic field of the Moon for more detail. On the terminator there could be significant horizontal electric fields forming between the day and night areas, resulting in horizontal dust transport.[20]

Also, the Moon has been shown to have a "sodium tail" too faint to be detected by the human eye. It is hundreds of thousands of miles long, and was discovered in 1998 as a result of Boston University scientists observing the Leonid meteor storm. The Moon is constantly releasing atomic sodium gas from its surface, and solar radiation pressure accelerates the sodium atoms in the anti-sunward direction, forming an elongated tail which points away from the Sun.[21][22][23] It has not yet been determined whether ionized sodium gas atoms or charged dust are the cause of the reported Moon glows.[24]

Chinese lander

China's Chang'e 3 spacecraft, which was launched on December 1, 2013, and entered lunar orbit on December 6,[25] was expected to contaminate the tenuous lunar exosphere with both propellant from engine firings and lunar dust from the vehicle's landing.[26] While concern was expressed that this could disrupt LADEE's mission,[26] such as its baseline readings of the Moon's exosphere, it may instead provide additional science value since both the quantity and composition of the spacecraft's propulsion system exhaust are known.[27] Data from LADEE may be used to track the distribution and eventual dissipation of the exhaust and dust in the Moon's exosphere.[27][28] It may also be possible to observe the migration of water, one component of the exhaust, giving insight on how it is transported and becomes trapped around the lunar poles.[29]

Mission objectives

The LADEE mission was designed to address three major science goals:[30]

and one technology demonstration goal:

Spaceflight operations

The Lunar Atmosphere and Dust Environment Explorer during liftoff
LADEE heads into orbit, as seen from Virginia (long-exposure photo)

Launch

LADEE was launched on September 7, 2013, at 03:27 UTC (September 6, 11:27 p.m. EDT), from the Wallops Flight Facility at the Mid-Atlantic Regional Spaceport on a Minotaur V carrier rocket.[32] This was the first lunar mission to be launched from that facility. The launch had the potential for visibility along much of the U.S. eastern seaboard, from Maine to South Carolina; clear weather allowed numerous observers from New York City to Virginia to observe the ascent, first stage cutoff and second stage ignition.[33]

As the Minotaur V is a solid-propellant rocket, spacecraft attitude control on this mission operated a bit differently from a typical liquid-fueled rocket with more continuous closed-loop feedback. The first three Minotaur stages "fly a pre-programmed attitude profile" to gain velocity and deliver the vehicle to its preliminary trajectory, while the fourth stage is used to modify the flight profile and deliver the LADEE spacecraft into perigee for the spin-stabilized fifth stage to then put the spacecraft into a highly elliptical orbit around Earth—the first of three—to begin a month-long Lunar transit.[34]

While now separated from the LADEE spacecraft, both the fourth and fifth stages of the Minotaur V reached orbit, and are now space debris in Earth orbit.[3]

Lunar transit

LADEE took an unusual approach in its transit of the Moon. Launched into a highly elliptical Earth orbit, the spacecraft made three increasingly larger laps around Earth[3] before getting close enough to enter into Lunar orbit. The transit required approximately one month.[35]

Artist concept of LADEE firing thrusters

After separating from the Minotaur, high electrical currents were detected in the satellite's reaction wheels causing them to be shut down. There was no indication of a fault, and after the protection limits were adjusted, orientation with reaction wheels was resumed the following day.[36]

LRO views LADEE about 9 km (5.6 mi) away orbiting the moon (January 14, 2014).

The LADEE spacecraft made three "phasing orbits" of Earth before it accomplished a Lunar orbit insertion (LOI), which occurred at perigee of the third orbit using a three-minute engine burn.[3] The target orbit for the third Earth orbit had a perigee of 200 kilometers (120 mi), an apogee of 278,000 km (173,000 mi) and an inclination of 37.65 degrees. The planned argument of perigee is 155 degrees, while its characteristic energy, C3 is -2.75 km2/s2.[3] The novel trajectory using orbital phasing loops was done for four main reasons:[37]

Lunar orbit and systems checkout

LADEE entered lunar orbit on October 6, 2013, when LADEE was put into an elliptical capture orbit of 24 hours duration.[38] LADEE was further lowered into a four-hour orbit on October 9, 2013,[39] One further burn occurred on October 12 lowering LADEE into a circular orbit around the Moon with an altitude of approximately 250 kilometers (160 mi) for its commissioning phase, which lasted about 30 days.[40] LADEE's systems and instruments were checked out after the orbit was lowered to 75 km (47 mi) altitude.[3]

Lunar Laser Communication Demonstration

Depiction of the optical module of the LLCD

LADEE's Lunar Laser Communication Demonstration (LLCD) pulsed laser system conducted a successful test on October 18, 2013, transmitting data between the spacecraft and its ground station on Earth at a distance of 385,000 kilometres (239,000 mi). This test set a downlink record of 622 megabits per second (Mbps) from spacecraft to ground, and an "error-free data upload rate of 20 Mbps" from ground station to spacecraft.[41][42]

The LLCD is a free-space optical communication system. It is NASA's first attempt at two-way space communication using an optical laser instead of radio waves. It is expected to lead to operational laser systems on future NASA satellites. The next iteration of the concept will be the Laser Communications Relay Demonstration scheduled for 2017.[41] Also, it has been proposed as payload for the Phobos And Deimos & Mars Environment (PADME) orbiter.[43]

Science phase

For the science operations, LADEE was maneuvered into an orbit with a periselene of 20 km (12 mi) and an aposelene of 60 km (37 mi).[1] The science phase of LADEE's primary mission was initially planned as 100 days,[3] and later given a 28-day extension. The extension provided an opportunity for the satellite to gather an additional full lunar cycle worth of very low-altitude data to help scientists unravel the nature of the Moon's tenuous exosphere.[44]

End of mission

Spacecraft controllers ordered a final engine burn on April 11, 2014, to lower LADEE to within 2 km (1 mi) of the Moon's surface and set it up for impact no later than April 21.[8][9][45] The probe then dealt with the April 2014 lunar eclipse on April 15, during which it could not generate power because it was in Earth's shadow for four hours.[46] Science instruments were turned off and heaters were cycled during the event to conserve energy but keep the spacecraft warm.[46] Engineers did not expect LADEE to survive, as it was not designed to handle such an environment, but it exited the eclipse with only malfunctions in some pressure sensors.[9]

During its penultimate orbit on April 17, LADEE's periapsis took it within 300 m (1,000 ft) of the lunar surface.[47] Contact with the spacecraft was lost around 04:30 UTC on April 18 when it moved behind the Moon.[8][48] LADEE struck the Moon's far side surface some time between 04:30 and 05:22 at a speed of 5,800 km/h (3,600 mph); scientists will attempt to narrow down the impact time and location.[9][47] The far side of the Moon was chosen to avoid the possibility of damaging historically important locations such as the Luna and Apollo landing sites.[8] NASA used the Lunar Reconnaissance Orbiter to image the impact location.[10][45][47]

LADEE - Impact Crater[10]
Before impact
After impact
Superimposed images
Sundman V crater (eastern rim); April 18, 2014

Spacecraft

Design

LADEE is the first spacecraft designed, integrated, built, and tested by NASA's Ames Research Center.[49] The spacecraft is of a novel design (a spacecraft bus never previously flown)—and of much lower cost than typical NASA science missions—which presented novel challenges to the trajectory design team in getting the new spacecraft launched to the Moon with a high-confidence spaceflight trajectory plan, while dealing with a first-use new rocket (Minotaur V) and a spacecraft with no flight test legacy. (see Lunar transit, above.)[49]

LADEE mission makes use of the Modular Common Spacecraft Bus, or body, made of a lightweight carbon composite with an unfueled mass of 248.2 kg (547 lb). The bus has the ability to perform on various kinds of missions—including voyages to the Moon and Near-Earth objects—with different modules or applicable systems. This modular concept is an innovative way of transitioning away from custom designs and toward multi-use designs and assembly-line production, which could dramatically reduce the cost of spacecraft development.[50] The LADEE spacecraft bus modules consist of the Radiator Module which carries the avionics, electrical system, and attitude sensors; the Bus Module; the Payload Module that carries the two largest instruments; and the Extension Modules, which house the propulsion system.[1]

Specifications

The main structure is 2.37 m (7.8 ft) high, 1.85 m (6.1 ft) wide and 1.85 m (6.1 ft) deep. The total mass of the spacecraft is 383 kg (844 lb).[1]

Power

Electrical power is generated by a photovoltaic system composed of 30 panels of silicon solar cells producing 295 W at one AU. The solar panels are mounted on the satellite's exterior surfaces and the electrical power is stored in one lithium-ion battery providing up to 24 amp-hours of 28-volt power.[1]

Propulsion system

The LADEE propulsion system consisted of an orbit control system (OCS) and a reaction control system (RCS). The OCS provided velocity control along the +Z axis for large velocity adjustments. The RCS provided three-axis attitude control during burns of the OCS system, and also provided momentum dumps for the reaction wheels which were the primary attitude control system between OCS burns.[32]

The main engine was a 455N High Performance Apogee Thruster (HiPAT). The high efficiency 22N attitude control thrusters are manufactured using high temperature materials and similar to the HiPAT. The main engine provided the majority of the thrust for spacecraft trajectory correction maneuvers. The control system thrusters were used for the small maneuvers planned for the science phase of the mission.[1]

Following the science phase, a decommissioning period occurred, during which the altitude was gradually lowered until the spacecraft impacted the lunar surface.[1]

Science payload

LADEE carried three scientific instruments and a technology demonstration payload.

The science payload consists of:[51]

LADEE also carried a technology demonstration payload for testing an optical communication system. The Lunar Laser Communication Demonstration (LLCD) used a laser to transmit and receive data as pulses of light, in much the same way as data is transferred in a fiber optic cable. Three ground stations were used. This method of communication could potentially provide data rates five times higher than the previous radio frequency communication system.[31][53] The technology is a direct predecessor to NASA's Laser Communications Relay Demonstration (LCRD) system which is due to launch in 2017.[54][55]

Preliminary results

The LADEE science teams continued to analyze data acquired at the time of the Chang'e 3 landing on December 14, 2013.[56]

Team

The team for LADEE includes contributors from NASA Headquarters, Washington D.C., NASA's Ames Research Center, Moffett Field, California, NASA's Goddard Space Flight Center, Greenbelt, Maryland, and the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder.[60] Guest investigators include those from the University of California, Berkeley;The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland; the University of Colorado; the University of Maryland; and NASA's Goddard Space Flight Center, Greenbelt, Maryland.[60]

Gallery

First images of the Moon captured by LADEE's star tracker, taken February 8, 2014.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 "Press Kit: Lunar Atmosphere and Dust Environment Explorer (LADEE) Launch" (PDF). NASA.gov. August 2013. Retrieved September 8, 2013.
  2. ↑ Garner, Rob (April 2, 2014). "LADEE Launch". NASA.gov. Retrieved April 19, 2014.
  3. 1 2 3 4 5 6 7 Graham, William (September 6, 2013). "Orbital's Minotaur V launches LADEE mission to the Moon". NASAspaceflight.com. Retrieved September 8, 2013.
  4. 1 2 3 Blau, Patrick. "LADEE - Mission and Trajectory Design". Spaceflight 101. Retrieved April 19, 2014.
  5. ↑ "LADEE Mission Overview". NASA.gov. September 6, 2013. Retrieved December 4, 2013.
  6. ↑ "Lunar Atmosphere and Dust Environment Explorer (LADEE)". National Space Science Data Center Master Catalog. NASA.
  7. ↑ "Missions - LADEE - NASA Science". NASA.
  8. 1 2 3 4 Chang, Kenneth (April 18, 2014). "With Planned Crash, NASA Lunar Mission Comes to End". The New York Times. Retrieved April 18, 2014.
  9. 1 2 3 4 Dunn, Marcia (April 18, 2014). "NASA's Moon-Orbiting Robot Crashes Down as Planned". ABC News. Retrieved April 18, 2014.
  10. 1 2 3 Neal-Jones, Nancy (October 28, 2014). "NASA’s LRO Spacecraft Captures Images of LADEE’s Impact Crater". NASA. Retrieved October 28, 2014.
  11. ↑ "NASA Sets Sights on Lunar Dust Exploration Mission". NASA. April 9, 2008. Retrieved September 8, 2013.
  12. ↑ Hine, Butler (April 30, 2013). "LADEE Project Manager Update". NASA.gov. Retrieved May 2, 2013.
  13. ↑ Hine, Butler (August 31, 2013). "LADEE Project Manager Update: LADEE Ready for Launch". NASA.gov. Retrieved September 3, 2013.
  14. ↑ Saravia, Claire (August 21, 2013). "NASA Goddard Plays Major Role in NASA Lunar Mission". NASA.gov. Retrieved August 21, 2013.
  15. ↑ "Moon Storms". Science.nasa.gov. December 7, 2005. Retrieved September 9, 2013.
  16. 1 2 Nelson, Robert. "Thomas Townsend Brown: Scientific Notebooks, Vol. 1". Rex Research.
  17. 1 2 "Moon Fountains". NASA. March 30, 2005.
  18. ↑ Stubbs, Timothy J.; Vondrak, Richard R.; Farrell, William M. (2005). "A Dynamic Fountain Model for Lunar Dust" (PDF). Lunar and Planetary Science XXXVI.
  19. ↑ "Strange Things Happen at Full Moon". LiveScience. Archived from the original on 2008-10-15.
  20. 1 2 "The Moon and the Magnetotail". NASA. May 16, 2008.
  21. ↑ "Moon's tail spotted". BBC. June 9, 1999. Retrieved November 15, 2009.
  22. ↑ "Astronomers discover that moon has long, comet-like tail". CNN. June 7, 1999. Retrieved December 18, 2007.
  23. ↑ "Lunar Leonids 2000". NASA. November 17, 2000. Retrieved December 18, 2007.
  24. ↑ "Is There an Atmosphere on the Moon?". NASA. April 12, 2013. Retrieved September 11, 2013.
  25. ↑ "Chang'e-3 enters lunar orbit". Xinhua. December 6, 2013. Retrieved December 6, 2013.
  26. 1 2 David, Leonard (November 21, 2013). "China's 1st Moon Lander May Cause Trouble for NASA Lunar Dust Mission". Space.com. Retrieved November 25, 2013.
  27. 1 2 Spudis, Paul D. (October 30, 2013). "Unplanned (But Controlled) Experiments: The Role of Serendipity". Air & Space / The Once and Future Moon. Retrieved December 6, 2013.
  28. ↑ David, Leonard (November 21, 2013). "China's 1st Moon Lander May Cause Trouble for NASA Lunar Dust Mission". Space. Retrieved December 7, 2013. LADEE also has the potential to measure dust that might be lofted above the lunar surface by the Chang'e 3 touchdown.
  29. ↑ Poore, Emily (December 2, 2013). "China Launches Lunar Mission". Sky & Telescope. Retrieved December 6, 2013.
  30. ↑ "NASA Solicitation: Instruments for LADEE Lunar Mission". SpaceRef. March 25, 2008. Retrieved July 30, 2011.
  31. 1 2 "Space Laser To Prove Increased Broadband Possible". NASA.
  32. 1 2 "Statement of Work - LADEE Spacecraft Propulsion System". NASA ARC. August 27, 2009.
  33. ↑ Boyle, Alan (September 6, 2013). "Watch NASA's LADEE moon launch on the East Coast – or online". NBC News. Retrieved September 12, 2013.
  34. ↑ "LADEE - Mission and Trajectory Design". Spaceflight 101. Retrieved September 21, 2013.
  35. ↑ Dunn, Marcia (September 7, 2013). "NASA launches robotic explorer to moon from Va.; trouble develops early in much-viewed flight". Star Tribune. Retrieved September 7, 2013.
  36. ↑ Clark, Stephen (September 7, 2013). "Moon mission blasts off, overcomes pointing problem". Spaceflight Now. Retrieved September 11, 2013.
  37. ↑ "Phasing Loops and the LADEE trajectory". The Astrogator's Guild. September 12, 2013. Retrieved October 18, 2013.
  38. ↑ "LADEE Update 10-07-13: Safe in Lunar Orbit after LOI-1". The Astrogator's Guild. October 7, 2013. Retrieved October 18, 2013.
  39. ↑ "LADEE Trajectory Update 10-9-13: LOI-2 nominal". The Astrogator's Guild. October 9, 2013. Retrieved October 18, 2013.
  40. ↑ Kramer, Miriam (October 7, 2013). "NASA's New Moon Probe Enters Lunar Orbit". Space.com. Retrieved October 18, 2013.
  41. 1 2 Messier, Doug (October 22, 2013). "NASA Laser System Sets Record with Data Transmissions From Moon". Parabolic Arc. Retrieved December 19, 2013.
  42. ↑ "Lunar Laser Communication Demonstration Reveals Bright Future For Space Communication". NASA (Red Orbit). December 24, 2013. Retrieved 2014-10-12.
  43. ↑ Reyes, Tim (1 October 2014). "Making the Case for a Mission to the Martian Moon Phobos". Universe Today. Retrieved 2014-10-05.
  44. ↑ Hoover, Rachel (January 31, 2014). "NASA Extends Moon Exploring Satellite Mission". NASA.gov. Retrieved February 21, 2014.
  45. 1 2 Brown, Dwayne; Hoover, Rachel; Washington, Dewayne (April 18, 2014). "NASA Completes LADEE Mission with Planned Impact on Moon's Surface". NASA.gov. Release 14-113. Retrieved April 18, 2014.
  46. 1 2 Skirble, Rosanne (April 18, 2014). "Robotic Mission Kicks Up Lunar Dust". Voice of America. Retrieved April 18, 2014.
  47. 1 2 3 Fuller-Wright, Liz (April 18, 2014). "Moon orbiter LADEE crashes triumphantly after 'amazing' mission". The Christian Science Monitor. Retrieved April 18, 2014.
  48. ↑ Brown, Dwayne; Hoover, Rachel (October 7, 2014). "NASA Lunar Mission Wins 2014 Popular Mechanics Breakthrough Award". NASA. Retrieved 2014-10-09.
  49. 1 2 Kramer, Miriam (September 9, 2013). "NASA Spacecraft Cruising to Moon With Novel Design". Space.com. Retrieved September 21, 2013.
  50. ↑ "LADEE Spacecraft". NASA.
  51. ↑ "LADEE's Science and Instruments". NASA. Retrieved July 26, 2015.
  52. ↑ "Lunar Dust Experiment (LDEX)". National Space Science Data Center. Retrieved July 26, 2015.
  53. ↑ "About LLCD | Goddard Space Flight Center". Esc.gsfc.nasa.gov. Retrieved September 9, 2013.
  54. ↑ "Laser communications set for Moon mission". ESA. July 7, 2013. Retrieved July 30, 2013.
  55. ↑ "NASA's First Laser Communication System Integrated, Ready for Launch". NASA. March 3, 2013. Retrieved July 30, 2013.
  56. 1 2 3 4 5 Elphic, Rick (January 31, 2014). "LADEE Project Scientist Update: Milestones, Maneuvers and Moisture?". NASA (Ames Research Center - NASA). Retrieved February 21, 2014.
  57. 1 2 Elphic, Rick (December 16, 2014). "LADEE Project Scientist Update: December 2014". NASA. Retrieved July 26, 2015.
  58. ↑ Elphic, R. C.; Hine, B.; Delory, G. T.; Salute, J. S.; Noble, S.; et al. (2014). The Lunar Atmosphere and Dust Environment Explorer (LADEE): Initial Science Results (PDF). 45th Lunar and Planetary Science Conference. The Woodlands, Texas. March 17–21, 2014. Lunar and Planetary Institute.
  59. ↑ Steigerwald, William (17 August 2015). "NASA's LADEE Spacecraft Finds Neon in Lunar Atmosphere". NASA. Retrieved 18 August 2015.
  60. 1 2 "Ladee Team - Nasa". Nasa.gov. August 27, 2013. Retrieved September 9, 2013.

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