Lucy (spacecraft)

Lucy is a planned NASA space probe that will complete a 12-year journey to seven different asteroids, visiting a main belt asteroid as well as six Jupiter trojans,[4] asteroids which share Jupiter's orbit around the Sun, orbiting either ahead of or behind the planet. All target encounters will be fly-by encounters.[5]

An artist's impression of the Lucy spacecraft performing a flyby of a Jupiter trojan.
NamesDiscovery Mission 13
Mission typeMultiple-flyby of asteroids
OperatorNASA Goddard · SwRI
Mission duration12 years (planned)
Spacecraft properties
ManufacturerLockheed Martin
Dimensions13 m (43 ft) in long [1]
Each solar panel: 6 m (20 ft) in diameter
Start of mission
Launch date16 October 2021 (planned) [2]
RocketAtlas V 401 [3]
Launch siteCape Canaveral, SLC-41
ContractorUnited Launch Alliance
High-resolution visible imager (L'LORRI)
Optical and near-infrared imaging spectrometer (L'Ralph)
Thermal infrared spectrometer (L'TES)
A diamond-shaped crest houses artworks of the Lucy fossil at left, the Lucy spacecraft at center, and an artist's impression of a Jupiter trojan. The word "Lucy" is written in a large, bold red font at the top right corner, while the words "First to the Trojans" and "SWRI · NASA · LM" are written in a smaller white font across the bottom edges of the diamond-shaped crest.
NASA patch for Lucy mission
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On 4 January 2017, Lucy was chosen, along with the Psyche mission, as NASA's Discovery Program missions 13 and 14 respectively.[5][6]

The mission is named after the 'Lucy' hominin skeleton, because the study of Trojans could reveal the "fossils of planet formation": materials that clumped together in the early history of the Solar System to form planets and other bodies.[7] The Australopithecus itself was named for a Beatles song, "Lucy in the Sky with Diamonds".[8]


The Jupiter trojan asteroids are shown in green.

Lucy is planned to launch in 2021 on the 401 variant of a United Launch Alliance Atlas V launch vehicle.[9] In 2025, it will fly by the inner main-belt asteroid 52246 Donaldjohanson, which was named for the discoverer of the Lucy hominin fossil.[10] In 2027, it will arrive at the L4 Trojan cloud (a group of asteroids that orbits about 60° ahead of Jupiter), where it will fly by four Trojans, 3548 Eurybates (with its satellite), 15094 Polymele, 11351 Leucus, and 21900 Orus.[5] After these flybys, Lucy will return to the vicinity of the Earth whereupon it will receive a gravity assist to take it to the L5 Trojan cloud (which trails about 60° behind Jupiter), where it will visit the binary Trojan 617 Patroclus with its satellite Menoetius in 2033. The mission may end with the Patroclus–Menoetius flyby, but at that point Lucy will be in a stable, 6-year orbit between the L4 and L5 clouds, and a mission extension will be possible.

Three instruments comprise the payload: a high-resolution visible imager, an optical and near-infrared imaging spectrometer and a thermal infrared spectrometer.[11] Harold F. Levison of the Southwest Research Institute in Boulder, Colorado is the principal investigator, with Catherine Olkin of Southwest Research Institute as the mission's deputy principal investigator. NASA's Goddard Space Flight Center will manage the project.

Exploration of Jupiter Trojans is one of the high priority goals outlined in the Planetary Science Decadal Survey. Jupiter Trojans have been observed by ground-based telescopes and the Wide-field Infrared Survey Explorer to be "dark with... surfaces that reflect little sunlight".[12] Jupiter is 5.2 AU (780×10^6 km; 480×10^6 mi) from the Sun, or about five times the Earth-Sun distance.[13] The Jupiter Trojans are at a similar distance but can be somewhat farther or closer to the Sun depending on where they are in their orbits. There may be as many Trojans as there are asteroids in the asteroid belt.[14]


NASA selected Lucy through the Discovery Program AO released on 5 November 2014.[15] Lucy was submitted as part of a call for proposals for the next mission(s) for Discovery Program that closed in February 2015. Proposals had to be ready to launch by the end of 2021. Twenty-eight proposals were received in all.

On 30 September 2015, Lucy was selected as one of five finalist missions, each of which received US$3 million to produce more in-depth concept design studies and analyses.[16][17][18][19] Its fellow finalists were DAVINCI, NEOCam, Psyche and VERITAS. On 4 January 2017, two of the five proposals — Lucy and Psyche — were selected for development and launch.

On 31 January 2019, NASA announced that Lucy would launch in October 2021 on an Atlas V 401 launch vehicle from Cape Canaveral, Florida. The total cost for the launch is estimated to be US$148.3 million.[3] On 11 February 2019, SpaceX protested the contract award, claiming that it could launch Lucy into the same orbit at a "significantly cheaper cost". On 4 April 2019, SpaceX withdrew the protest.[20]

On 28 August 2020, NASA announced that Lucy had passed its Key Decision Point-D (KDP-D) milestone. The Lucy engineers have a "green light" to assemble and test the spacecraft and its instruments. The spacecraft instruments are expected to arrive beginning in October, which will see the Mission Operation Review procedural milestone. By July 2021, the spacecraft should be ready to head to Florida for its launch preparations. Lucy's launch window opens on 16 October 2021, and the spacecraft will make its first asteroid flyby in April 2025.[21]

Science payloadEdit

The science payload includes:[1][16]

  • L'TES - thermal infrared spectrometer (6-75 μm). L'TES is similar to OTES on the OSIRIS-REx mission and will be built at Arizona State University. It will reveal the thermal characteristics of the observed Trojans, which will also inform the composition and structure of the material on the surface of the asteroids.
  • The radio science investigation will determine the mass of the Trojans by using the spacecraft radio telecommunications hardware and high-gain antenna to measure Doppler shifts.


Targets with their flyby dates include:[10][22][23][24]

Date Target Group Diameter Type
20 April 2025 52246 Donaldjohanson Inner main belt, member of ~130 Myr old Erigone family 4 km C-type asteroid. Lucy will flyby the asteroid from 922 km.
12 August 2027 3548 Eurybates Greek camp at L4 64 km (satellite: 1km) C-type asteroid, largest member of the only confirmed disruptive collisional family in the Trojans. Has a small satellite.
15 September 2027 15094 Polymele Greek camp at L4 21 km P-type asteroid that may be a collisional fragment of a larger P-type asteroid. Its red color suggests surface is rich in organic compounds called tholins.
18 April 2028 11351 Leucus Greek camp at L4 34 km D-type asteroid, slow rotator taking 466 hours per rotation.
11 November 2028 21900 Orus Greek camp at L4 51 km Characterized as a D-type and C-type asteroid by the Lucy mission team and by Pan-STARRS photometric survey, respectively. Possible binary.[25]
2 March 2033 617 Patroclus Trojan camp at L5 Patroclus: 113 km
Menoetius: 104 km
They are binary P-type asteroids.[26] The pair orbit at a separation of 680 km.
Lucy will alternate visiting Jupiter's Greek (L4) and Trojan camps (L5) every six years.

See alsoEdit


  1. ^ a b "The Lucy Spacecraft and Payload". Southwest Research Institute. 9 July 2018.
  2. ^ - page 427-433 - 10 February 2020   This article incorporates text from this source, which is in the public domain.
  3. ^ a b "NASA Awards Launch Services Contract for Lucy Mission". NASA. 31 January 2019.   This article incorporates text from this source, which is in the public domain.
  4. ^ Hille, Karl (21 October 2019). "NASA's Lucy Mission Clears Critical Milestone". NASA. Retrieved 5 December 2020.   This article incorporates text from this source, which is in the public domain.
  5. ^ a b c Chang, Kenneth (6 January 2017). "A Metal Ball the Size of Massachusetts That NASA Wants to Explore". The New York Times.
  6. ^ Northon, Karen (4 January 2017). "NASA Selects Two Missions to Explore the Early Solar System". NASA.   This article incorporates text from this source, which is in the public domain.
  7. ^ Witze, Alexandra (16 March 2015). "Five Solar System sights NASA should visit". Nature.
  8. ^ Johanson, Donald C.; Wong, Kate (2010). Lucy's Legacy: The Quest for Human Origins. Crown Publishing Group. pp. 8–9. ISBN 978-0-307-39640-2.
  9. ^   This article incorporates text from this source, which is in the public domain.
  10. ^ a b Dreier, Casey; Lakdawalla, Emily (30 September 2015). "NASA announces five Discovery proposals selected for further study". The Planetary Society.
  11. ^ Leibold, Rob (2 October 2015). "SwRI awarded US$3 million NASA contract to develop mission to Jupiter's Trojan asteroids" (Press release). Southwest Research Institute.
  12. ^ "PIA16211: Trojan Colors Revealed (Artist's Concept)". NASA. 15 October 2012.   This article incorporates text from this source, which is in the public domain.
  13. ^ Wall, Jennifer (1 June 2015). "What Is Jupiter?". NASA.   This article incorporates text from this source, which is in the public domain.
  14. ^ Dreier, Casey; Lakdawalla, Emily (30 September 2015). "NASA announces five Discovery proposals selected for further study". The Planetary Society.
  15. ^ - p. 432/817 - 10 February 2020   This article incorporates text from this source, which is in the public domain.
  16. ^ a b Leibold, Rob (2 October 2015). "SwRI Awarded US$3 Million NASA Contract To Develop Mission To Jupiter's Trojan Asteroids" (Press release). Southwest Research Institute.
  17. ^ Brown, Dwayne C.; Cantillo, Laurie (30 September 2015). "NASA Selects Investigations for Future Key Planetary Mission". NASA.   This article incorporates text from this source, which is in the public domain.
  18. ^ Clark, Stephen (24 February 2014). "NASA receives proposals for new planetary science mission". Spaceflight Now.
  19. ^ Kane, Van (2 December 2014). "Selecting the Next Creative Idea for Exploring the Solar System". The Planetary Society.
  20. ^ Foust, Jeff (5 April 2019). "SpaceX drops protest of NASA launch contract". SpaceNews.
  21. ^ Bartels, Meghan (31 August 2020). "NASA asteroid mission Lucy begins spacecraft assembly before 2021 launch". SpaceNews.
  22. ^ "Lucy: Surveying the Diversity of Trojan Asteroids, the Fossils of Planet Formation" (PDF). Southwest Research Institute. 2015. Retrieved 11 July 2017.
  23. ^ Levison, H. F.; Olkin, C.; Noll, K. S.; Marchi, S. (March 2017). Lucy: Surveying the Diversity of the Trojan Asteroids, the Fossils of Planet Formation (PDF). 48th Lunar and Planetary Science Conference. 20–24 March 2017 The Woodlands, Texas. Bibcode:2017LPI....48.2025L. LPI Contribution No. 1964, id. 2025.
  24. ^ "Mission Targets". Lucy. Southwest Research Institute. 25 June 2018.
  25. ^ Noll, K. S.; Grundy, W. M.; Buie, M. W.; Levison, H. F.; Olkin, C.; Marchi, S.; Brown, M. E.; Mottola, S. (22 August 2018), 15622 - Confirmation of a Binary Companion to 21900 Orus (PDF), Space Telescope Science Institute
  26. ^ Sanders, Robert (1 February 2006). "Binary asteroid in Jupiter's orbit may be icy comet from solar system's infancy" (Press release). University of California Berkeley.

External linksEdit