|
Mission
type
|
Multi-target orbiter
|
|
Operator
|
|
|
2007-043A
|
|
|
Website
|
|
|
Mission
duration
|
~9 years[1]
|
|
Spacecraft
properties
|
|
|
Manufacturer
|
Orbital Sciences · JPL(Jet Propulsion
Laboratory) · UCLA(University of California, Los
Angeles)
|
|
1,240 kg (2,730 lb)
(wet)[2]
|
|
|
Power
|
1300 W (Solar
array) at 3 AU[2]
|
|
Start of
mission
|
|
|
Launch
date
|
|
|
Rocket
|
|
|
Launch
site
|
|
|
Flyby of
Mars (Gravity assist)
|
|
|
Closest
approach
|
February 4, 2009
(6 years, 1 month and 6 days ago) |
|
Distance
|
549 km (341 mi)
|
|
4 Vesta
orbiter
|
|
|
Orbital
insertion
|
July 16, 2011 04:47 UTC[4]
(3 years, 7 months and 22 days ago) |
|
Departed
orbit
|
September 5, 2012
(2 years, 6 months and 5 days ago) |
|
Ceres orbiter
|
|
|
Orbital
insertion
|
March 6, 2015[5]
|
 |
|
Dawn is a space probe launched by NASA in 2007 to study
the two most massive protoplanets of the asteroid
belt: Vesta
and the dwarf
planet Ceres.[6]
Dawn has been taking high-resolution images of Ceres since December 1,
2014,[5][7]
and entered orbit around Ceres on March 6, 2015.[8][9]
Dawn was the first spacecraft to visit Vesta, entering orbit
on July 16, 2011, and successfully completed its 14-month Vesta survey mission
in late 2012.[10][11]
Dawn is the first spacecraft to visit Ceres, to orbit a dwarf planet and
to orbit two separate extraterrestrial bodies.[8]
The mission is managed by NASA's Jet Propulsion Laboratory, with major
components contributed by European partners from the Netherlands, Italy and
Germany. It is the first NASA exploratory mission to use ion
propulsion to enter orbits; previous multi-target missions using
conventional drives, such as the Voyager
program, were restricted to flybys.[2]
Contents
- 1 Project history
- 2 Scientific background
- 3 Objectives
- 4 Specifications
- 5 Mission summary
- 5.1 Launch preparations
- 5.2 Launch
- 5.3 Transit (Earth to Vesta)
- 5.4 Vesta approach
- 5.5 Vesta orbit
- 5.6 Transit (Vesta to Ceres)
- 5.7 Ceres approach
- 5.8 Ceres orbit
- 5.9 Mission conclusion
- 6 See also
- 7 References
- 8 External links
Project history
Initial cancellations
The
status of the Dawn mission changed several times. The project was
cancelled in December 2003,[12]
and then reinstated in February 2004. In October 2005, work on Dawn was
placed in "stand down" mode, and in January 2006, the mission was
discussed in the press as "indefinitely postponed", even though NASA
had made no new announcements regarding its status.[13]
On March 2, 2006, Dawn was again cancelled by NASA.[14]
Reinstatement
The
spacecraft's manufacturer, Orbital Sciences Corporation, appealed
NASA's decision, offering to build the spacecraft at cost, forgoing any profit
in order to gain experience in a new market field. NASA then put the
cancellation under review,[15]
and on March 27, 2006, it was announced that the mission would not be cancelled
after all.[16][17]
In the last week of September 2006, the Dawn mission's instrument
payload integration reached full functionality. Although originally projected
to cost US$373 million, cost overruns inflated the final cost of the mission to
US$446 million in 2007.
Scientific background
True-to-scale comparison of Vesta,
Ceres, and Earth's moon
The
Dawn mission was designed to study two large bodies in the asteroid
belt in order to answer questions about the formation of the Solar
System, as well as to test the feasibility of its ion
drive. Ceres and Vesta were chosen as two contrasting protoplanets,
the first one apparently "wet" (i.e. icy and cold) and the other
"dry" (i.e. rocky), whose accretion was terminated by the formation
of Jupiter.
The two bodies provide a bridge in scientific understanding between the
formation of rocky planets and the icy bodies of the Solar
System, and under what conditions a rocky planet can hold water.[19]
The
International Astronomical Union
(IAU) adopted a new definition of planet on August 24, 2006,
which introduced the term "dwarf
planet" for ellipsoidal worlds that were too small to
qualify for planetary status by "clearing their orbital
neighborhood" of other orbiting matter. If it succeeds, Dawn
will be the first mission to study a dwarf planet, arriving at Ceres a few
months before the arrival of the New
Horizons probe at Pluto in July 2015.
Ceres
is a dwarf planet whose mass comprises about one-third of the total mass of the
bodies in the asteroid belt, and whose spectral characteristics suggest a
composition similar to that of a water-rich carbonaceous chondrite.[20]
Vesta, a smaller, water-poor achondritic asteroid, has experienced significant heating and differentiation. It shows signs of a
metallic core, a Mars-like density and lunar-like basaltic flows.[21]
Dawn image of Ceres from 46,000 km, 19 February 2015
Available
evidence indicates that both bodies formed very early in the history of the
Solar System, thereby retaining a record of events and processes from the time
of the formation of the terrestrial planets. Radionuclide
dating of pieces of meteorites thought to come from Vesta suggests that Vesta
differentiated quickly, in three million years or less. Thermal evolution
studies suggest that Ceres must have formed some time later, more than three
million years after the formation of CAIs (the oldest known objects of Solar
System origin).[21]
Moreover,
Vesta appears to be the source of many smaller objects in the Solar System.
Most (but not all) V-type near-Earth asteroids, and some outer main-belt
asteroids, have spectra
similar to Vesta, and are thus known as vestoids. Five percent of the
meteoritic samples found on Earth, the howardite–eucrite–diogenite
(HED) meteorites, are thought to be the result of a collision or collisions
with Vesta.
It
is thought that Ceres may have a differentiated interior;[22]
its oblateness appears too small for an undifferentiated body, which indicates
that it consists of a rocky core overlain with an icy mantle.[22]
There is a large collection of potential samples from Vesta accessible to
scientists, in the form of over 1,400 HED
meteorites,[23]
giving insight into Vestan geologic history and structure. Vesta is thought to
consist of a metallic iron–nickel core, an overlying rocky olivine mantle
and crust.[24][25][26]
Objectives
A Dawn image of Vesta from
orbit
Dawn 's approximate flight trajectory
The
Dawn mission's goal is to characterize the conditions and processes of
the Solar
System's earliest eon by investigating in detail two of the largest protoplanets
remaining intact since their formation.[27]
The primary question that the mission addresses is the role of size and water
in determining the evolution of the planets.[27]
Ceres and Vesta are highly suitable bodies with which to address this question,
as they are two of the most massive of the protoplanets. Ceres is geologically
very primitive and icy, while Vesta is evolved and rocky. Their contrasting
characteristics are thought to have resulted from them forming in two different
regions of the early Solar System.[27]
There
are three principal scientific drivers for the mission. First, the Dawn
mission can capture the earliest moments in the origin of the Solar System,
granting an insight into the conditions under which these objects formed.
Second, Dawn determines the nature of the building blocks from which the
terrestrial planets formed, improving scientific understanding of this
formation. Finally, it contrasts the formation and evolution of two small
planets that followed very different evolutionary paths, allowing scientists to
determine what factors control that evolution.[27]
Specifications
Dimensions
With
its solar
array in the retracted launch position, the Dawn spacecraft is 2.36
meters (7.7 ft) long. With its solar arrays fully extended, Dawn is
19.7 m (65 ft) long.[28]
Total area of solar arrays is 36.4 m2 (392 sq ft).[29]
Propulsion system
Dawn 's solar array at full extension
The
Dawn spacecraft is propelled by three xenon ion
thrusters that inherited NSTAR
engineering technology from the Deep
Space 1 spacecraft.[30]
They have a specific impulse of 3,100 s and produce a thrust of
90 mN.[31]
The whole spacecraft, including the ion propulsion thrusters, is powered by a
10 kW (at 1 au) triple-junction gallium
arsenide photovoltaic solar array manufactured by Dutch
Space.[32][33]
To get to Vesta, Dawn was allocated 275 kg (606 lb) of xenon,
with another 110 kg (243 lb) to reach Ceres,[34]
out of a total capacity of 425 kg (937 pounds) of on-board propellant.[35]
With the propellant it carries, Dawn can perform a velocity change
of more than 10 km/s over the course of its mission, far more than any
previous spacecraft achieved with onboard propellant after separation from its
launch rocket.[34]
Dawn is NASA's first purely exploratory mission to use ion propulsion
engines.[36]
The spacecraft also has twelve 0.9 N hydrazine
thrusters for attitude control, which can assist in orbital insertion.[37]
Microchip
Dawn carries a memory chip bearing the names of more than 360,000
space enthusiasts.[38]
The names were submitted online as part of a public outreach effort between
September 2005 and November 4, 2006.[39]
The microchip, which is two centimetres in diameter, was installed on May 17,
2007, above the spacecraft's forward ion thruster, underneath its high-gain
antenna.[40]
More than one microchip was made, with a back-up copy put on display at the
2007 Open House event at the Jet Propulsion Laboratory in Pasadena, California.
Payload
Dawn prior to encapsulation at its launch pad on July 1, 2007
NASA's
Jet Propulsion Laboratory provided overall planning and management of the
mission, the flight system and scientific payload development, and provided the
Ion Propulsion System. Orbital Sciences Corporation provided
the spacecraft, which constituted the company's first interplanetary mission.
The Max Planck Institute for
Solar System Research and the German Aerospace Center (DLR) provided the
framing cameras, the Italian Space Agency provided the mapping spectrometer,
and the Los Alamos National Laboratory
provided the gamma
ray and neutron
spectrometer.[2]
- Framing camera (FC) — The framing camera uses 20 mm aperture, f/7.9 refractive optical system with a focal length of 150 mm.[41][42] A frame-transfer charge-coupled device (CCD), a Thomson TH7888A,[42] at the focal plane has 1024 × 1024 sensitive 93-Îŧrad pixels, yielding a 5.5° x 5.5° field of view. An 8-position filter wheel permits panchromatic (clear filter) and spectrally selective imaging (7 narrow band filters). The broadest filter allows imaging at wavelengths ranging from 400 to 1050 nm. In addition, the framing camera will acquire images for optical navigation while in the vicinities of Vesta and Ceres. The FC computer is a custom radiation-hardened Xilinx system with a LEON2 core and 8 GiB of memory.[42] The camera will offer resolutions of 17 m/pixel for Vesta and 66 m/pixel for Ceres.[42] Because the framing camera is vital for both science and navigation, the payload has two identical and physically separate cameras (FC1 & FC2) for redundancy, each with its own optics, electronics, and structure.[2][43]
Diagram showing the location of
various key components on the Dawn spacecraft bus
- Visible and infrared spectrometer (VIR) — This instrument is a modification of the visible and infrared thermal-imaging spectrometer used on the Rosetta and Venus Express spacecraft. It also draws its heritage from the Saturn orbiter Cassini's visible and infrared mapping spectrometer. The spectrometer's VIR spectral frames are 256 (spatial) × 432 (spectral), and the slit length is 64 mrad. The mapping spectrometer incorporates two channels, both fed by a single grating. A CCD yields frames from 0.25 to 1.0 Îŧm, while an array of HgCdTe photodiodes cooled to about 70K spans the spectrum from 0.95 to 5.0 Îŧm.[2][44]
- Gamma Ray and Neutron Detector (GRaND) — This instrument is based on similar instruments flown on the Lunar Prospector and Mars Odyssey space missions. This instrument includes 21 sensors with a very wide field of view.[41] It will be used to measure the abundances of the major rock-forming elements (oxygen, magnesium, aluminium, silicon, calcium, titanium, and iron) on Vesta and Ceres, as well as potassium, thorium, uranium, and water (inferred from hydrogen content).[45][46][47][48][49][50]
A
magnetometer
and laser altimeter
were considered for the mission, but were not ultimately flown.[51]
Mission summary
Launch preparations
On
April 10, 2007, the spacecraft arrived at the Astrotech Space Operations
subsidiary of SPACEHAB,
Inc. in Titusville, Florida, where it was prepared for
launch.[52][53]
The launch was originally scheduled for June 20, but was delayed until June 30
due to delays with part deliveries.[54]
A broken crane at the launch pad, used to raise the solid rocket boosters, further delayed the
launch for a week, until July 7; prior to this, on June 15, the second stage
was successfully hoisted into position.[55]
A mishap at the Astrotech Space Operations facility, involving slight damage to
one of the solar arrays, did not have an effect on the launch date; however,
bad weather caused the launch to slip to July 8. Range tracking problems then
delayed the launch to July 9, and then July 15. Launch planning was then suspended
in order to avoid conflicts with the Phoenix mission to Mars, which was
successfully launched on August 4.
Launch
Dawn launching on a Delta II
rocket from Cape Canaveral
Air Force Station Space Launch Complex 17 on September 27, 2007
The
launch of Dawn was rescheduled for September 26, 2007,[56][57][58]
then September 27, due to bad weather delaying fueling of the second stage, the
same problem that delayed the July 7 launch attempt. The launch window extended
from 07:20–07:49 EDT (11:20–11:49 GMT).[59]
During the final built-in hold at T−4 minutes, a ship entered the exclusion
area offshore, the strip of ocean where the rocket boosters were likely to fall
after separation. After commanding the ship to leave the area, the launch was required
to wait for the end of a collision avoidance window with the International Space Station.[60]
Dawn finally launched from pad 17-B
at the Cape Canaveral Air Force Station
on a Delta
7925-H rocket[61]
at 07:34 EDT,[62][63][64]
reaching escape velocity with the help of a spin-stabilized solid-fueled third
stage.[65][66]
Thereafter, Dawn's ion thrusters took over.
Transit (Earth to Vesta)
After
initial checkout, during which the ion
thrusters accumulated more than 11 days of thrust, Dawn began
long-term cruise propulsion on December 17, 2007.[67]
On October 31, 2008, Dawn completed its first thrusting phase to send it
on to Mars for a gravity assist flyby in February 2009. During this
first interplanetary cruise phase, Dawn spent 270 days, or 85% of this
phase, using its thrusters. It expended less than 72 kilograms of xenon propellant
for a total change in velocity of 1.81 kilometers per second. On November 20,
2008, Dawn performed its first trajectory
correction maneuver (TCM1), firing its number 1 thruster for 2 hours, 11
minutes.
Greyscale NIR image of Mars
(northwest Tempe Terra), taken by Dawn during its 2009
flyby
Dawn made its closest approach (549 km) to Mars on February 17,
2009 during a successful gravity assist.[68][69]
On this day, the spacecraft placed itself in safe mode, resulting in some data
acquisition loss. The spacecraft was reported to be back in full operation two
days later, with no impact on the subsequent mission identified. The root cause
of the event was reported to be a software programming error.[70]
To
cruise from Earth to its targets, Dawn traveled in an elongated outward
spiral trajectory. NASA posts and continually updates the current location and
status of Dawn online.[71]
The actual Vesta chronology and estimated Ceres chronology are as follows:[1]
- September 27, 2007: launch
- February 17, 2009: Mars gravity assist
- July 16, 2011: Vesta arrival and capture
- August 11–31, 2011: Vesta survey orbit
- September 29, 2011 – November 2, 2011: Vesta first high altitude orbit
- December 12, 2011 – May 1, 2012: Vesta low altitude orbit
- June 15, 2012 – July 25, 2012: Vesta second high altitude orbit
- September 5, 2012: Vesta departure
- March 6, 2015: Ceres arrival
- Early 2016: End of primary Ceres operations
Vesta approach
As
Dawn approached Vesta, the Framing Camera instrument took progressively
higher-resolution images, which were published online and at news conferences
by NASA
and MPI.
Vesta
from 265,000 km, June 14, 2011
Vesta
from 152,000 km, June 24, 2011
Vesta
from 100,000 km, July 1, 2011
Vesta
from 41,000 km, July 9, 2011
On
May 3, 2011, Dawn acquired its first targeting image, 1,200,000 km
from Vesta, and began its approach phase to the asteroid.[72]
On June 12, Dawn's speed relative to Vesta was slowed in preparation for
its orbital insertion 34 days later.[73][74]
Dawn was scheduled to be inserted into orbit at 05:00 UTC on
July 16 after a period of thrusting with its ion engines. Because its antenna
was pointed away from the Earth during thrusting, scientists were not able to
immediately confirm whether or not Dawn successfully made the maneuver.
The spacecraft would then reorient itself, and was scheduled to check in at
06:30 UTC on July 17.[75]
NASA later confirmed that it received telemetry from Dawn indicating
that the spacecraft successfully entered orbit around Vesta.[76]
The exact time of insertion could not be confirmed, since it depended on
Vesta's mass distribution, which was not precisely known and at that time had
only been estimated.[77]
Vesta orbit
After
being captured by Vesta's gravity and entering its orbit on July 16, 2011,[78]
Dawn moved to a lower, closer orbit by running its xenon-ion engine
using solar power. On August 2, it paused its spiralling approach to enter a
69-hour survey orbit at an altitude of 2,750 km. It assumed a 12.3-hour
high-altitude mapping orbit at 680 km on September 27, and finally entered
a 4.3-hour low-altitude mapping orbit at 210 km on December 8. Image
from 5,200 km, July 24, 2011
In
May 2012, NASA released the preliminary results of Dawn 's study of
Vesta, including estimates of the size of Vesta's metal-rich core, which is
theorized to be 220 km across. NASA scientists furthermore stated that
they think that Vesta is the "last of its kind" – the only remaining
example of the large planetoids that came together to form the rocky planets
during the formation of the Solar System.[78][82][83]
In October 2012, NASA stated that data from Dawn had revealed the origin
of anomalous dark spots and streaks on Vesta's surface, which were likely
deposited by ancient asteroid impacts.[84][85][86]
In December 2012, it was reported that Dawn had observed gullies on the
surface of Vesta that were interpreted to have been eroded by transiently
flowing liquid water.[87][88]
More details about the Dawn mission’s scientific discoveries at Vesta are
included on the Vesta
page.
Dawn was originally scheduled to depart Vesta and begin its two
and a half year journey to Ceres on August 26, 2012.[11]
However, a problem with one of the spacecraft's reaction
wheels forced Dawn to delay its departure from Vesta's gravity until
September 5, 2012.[10][89][90][91][92]
Results
|
Geologic Map of Vesta.[93]
|
The most ancient and heavily cratered regions are brown;
areas modified by the Veneneia
and Rheasilvia impacts are purple
(the Saturnalia Fossae Formation, in the north)[94] and light cyan (the
Divalia Fossae Formation, equatorial),[93] respectively; the
Rheasilvia impact basin interior (in the south) is dark blue, and neighboring
areas of Rheasilvia ejecta (including an area within Veneneia) are light
purple-blue;[95][96] areas modified by
more recent impacts or mass wasting are yellow/orange or green, respectively.
|
Transit (Vesta to Ceres)
During
its time in orbit around Vesta the probe experienced failures of reaction
wheels. Investigators will modify their activities upon arrival at Ceres for
close range geographical survey mapping. The Dawn team will orient the
probe by what they have stated is a "hybrid" mode. This mode will
utilize both reaction wheels and ion thrusters. Engineers have determined that
the hybrid mode will conserve fuel. On November 13, 2013, during the transit,
in a test preparation, Dawn engineers completed a 27-hour-long series of
exercises of said hybrid mode.[97]
On
September 11, 2014, Dawn's ion thrusting unexpectedly halted and the
probe began operating in a triggered safe mode. To avoid a lapse in propulsion,
the mission team hastily exchanged the active ion engine and electrical
controller with another. The team stated that they had a plan in place to
revive this disabled component later in 2014. The controller in the ion
propulsion system may have been damaged by a high-energy particle of radiation.
Upon exiting the safe mode on September 15, the probe resumed normal ion
thrusting.[98]
Further,
the Dawn investigators also found that they could not aim the main
communications antenna towards Earth. Another antenna of weaker capacity was
instead retasked. To correct the problem the probe's computer was reset and the
aiming mechanism of the main antenna was restored.
Ceres approach
Dawn began photographing an extended disk of Ceres on December
1, 2014,[7]
with images of partial rotations on January 13 and 25, 2015 released as
animations. Images taken from Dawn of Ceres after January 26 exceed the
resolution of the Hubble Space Telescope,[99]
while images taken of Pluto by New Horizons will exceed the resolution
of the Hubble telescope by approximately May 5, 2015.[100]
Progression of images of Ceres by Dawn
between January and February 2015
From 29,000 miles (46,000 kilometers) away on February 19, 2015
Because
of the failure of two reaction wheels, Dawn will make fewer camera
observations of Ceres during its approach phase than it did during its Vesta
approach. Camera observations require turning the spacecraft, which consumes
precious hydrazine fuel. Seven optical navigation photo sessions (OpNav 1–7, on
January 13 and 25, February 3 and 25, March 1, and April 10 and 15) and two
full rotation observation sessions (RC1–2, on February 12 and 19) are planned
before full observation begins with orbital capture. The gap in March and early
April is when Ceres appears too close to the sun from Dawn 's vantage
point to take pictures safely.[101]
Dawn entered Ceres orbit on March 6, 2015,[5]
four months prior to the arrival of New
Horizons at Pluto;
Dawn is thus the first mission to study a dwarf
planet at close range.[102][103]
|
Imaging dates (2014–2015) and
resolution[104]
|
||||
|
Date
|
distance
(km) |
diameter
(px) |
resolution
(km/px) |
portion
of disk
illuminated |
|
December 1
|
1,200,000
|
9
|
112
|
94%
|
|
January 13
|
383,000
|
27
|
36
|
95%
|
|
January 25
|
237,000
|
43
|
22
|
96%
|
|
February 3
|
146,000
|
70
|
14
|
97%
|
|
February 12
|
83,000
|
122
|
7.8
|
98%
|
|
February 19
|
46,000
|
222
|
4.3
|
87%
|
|
February 25
|
40,000
|
255
|
3.7
|
44%
|
|
March 1
|
49,000
|
207
|
4.6
|
23%
|
|
April 10
|
33,000
|
306
|
3.1
|
17%
|
|
April 15
|
22,000
|
453
|
2.1
|
49%
|
Ceres orbit
Dawn 's mission profile calls for it to enter polar orbit
around Ceres[when?] at an
initial altitude of 13,500 km for a first full characterization (RC3). One
RC3 orbit will take 15 days, during which Dawn will alternate taking
pictures and sensor measurements and then relaying the resulting data back to
Earth.[105]
Dawn will then spiral down to a survey orbit at an altitude of
4,430 km. This phase will last for 22 days, and is designed to obtain a
global view of Ceres with Dawn 's framing camera, and global maps with
the visible and infrared mapping spectrometer (VIR). Dawn will then
spiral down to an altitude of 1,480 km, where in August 2015 it will begin
a two-month phase known as the high-altitude mapping orbit. During this phase, Dawn
will continue to acquire near-global maps with the VIR and framing camera at
higher resolution than in the survey phase. It will also image in stereo to
resolve the surface in 3D. After spiralling down for another two months, Dawn
will begin its closest orbit around Ceres in late November 2015, at a distance
of about 375 km. This orbit is designed to acquire data for three months
with Dawn's gamma-ray and neutron detector (GRaND) and gravity investigation.[102]
Mission conclusion
It
was initially hoped that after the primary mission, a flyby of the remaining
protoplanet in the asteroid belt, Pallas, might
be possible when it crosses the ecliptic in 2018. (Because of the high inclination of the
Palladian orbit, only a quick flyby would have been possible.) However, with
two of Dawn's reaction wheels out of commission, the remainder of Dawn's
hydrazine fuel will need to be expended to orient the craft in low Cererian
orbit.[106]
The supply of hydrazine will dictate the length of the primary mission; it will
not be possible for Dawn to leave Ceres. Dawn will become a
long-term satellite of Ceres when the hydrazine fuel is exhausted, with orbital
stability on a time scale of centuries.[107]
References
1.
· "GSpace Topics:
Dawn". Retrieved November 9, 2013.
· · Rayman, Marc;
Fraschetti, Raymond, Russell (April 5, 2006). "Dawn: A mission
in development for exploration of main belt asteroids Vesta and Ceres".
Acta Astronautica 58 (11): 605–616. Bibcode:2006AcAau..58..605R.
doi:10.1016/j.actaastro.2006.01.014.
Retrieved April 14, 2011.
· · "NASA's
Dawn Spacecraft Begins Science Orbits of Vesta". NASA. August 1, 2011.
Retrieved August 6, 2011.
· · Alan Boyle (March 6,
2015), Dawn
Spacecraft Slips Quietly Into Orbit Around Dwarf Planet Ceres, NBC News,
retrieved March 6, 2015
· · Landau, Elizabeth;
Brown, Dwayne (March 6, 2015). "NASA Spacecraft
Becomes First to Orbit a Dwarf Planet". NASA. Retrieved March
6, 2015.
· · Rayman, Marc (6
March 2015). "Dawn
Journal: Ceres Orbit Insertion!". Planetary
Society. Retrieved 6 March 2015.
· · "NASA's
Dawn Spacecraft Hits Snag on Trip to 2 Asteroids". Space.com. August
15, 2012. Retrieved August 27, 2012.
· · Ambrosiano, Nancy
(March 28, 2006). "NASA's
Dawn mission is a go". Los Alamos National Laboratory. Retrieved October
1, 2007.
· · Chang, Alicia
(2006). "NASA
Asteroid Mission Won't Launch This Year". Space.com. Retrieved March
4, 2006.
· · Clark, Stephen
(2006). "Probe
built to visit asteroids killed in budget snarl". SpaceflightNow.com.
Retrieved March 4, 2006.
· · "NASA
reviewing canceled mission". CNN.com. March 16, 2006. Archived from the
original on March 21, 2006. Retrieved March 27, 2006.
· · Malik, Tariq (March
27, 2006). "NASA
Reinstates Cancelled Asteroid Mission". Space.com. Retrieved March 27,
2006.
· · Thomas B. McCord and
Christophe Sotin (2005). "Ceres: Evolution and current state". Journal
of Geophysical Research 110 (E5): E05009. Bibcode:2005JGRE..11005009M.
doi:10.1029/2004JE002244.
· · Thomas, P. C.;
Parker, J. Wm.; McFadden, L. A.; Russell, C. T.; Stern, S. A.; Sykes, M. V.;
Young, E. F. (2005). "Differentiation of the asteroid Ceres as revealed by
its shape". Nature 437 (7056): 224–6. Bibcode:2005Natur.437..224T.
doi:10.1038/nature03938. PMID 16148926.
· · Ghosh, A; McSween,
Harry Y. (1998). "A Thermal Model for the Differentiation of Asteroid 4
Vesta, Based on Radiogenic Heating". Icarus 134 (2): 187. Bibcode:1998Icar..134..187G.
doi:10.1006/icar.1998.5956.
· · Sahijpal, S.; Soni,
P.; Gagan, G. (2007). "Numerical simulations of the differentiation of
accreting planetesimals with 26Al and 60Fe as the heat
sources". Meteoritics & Planetary Science 42 (9):
1529–1548. Bibcode:2007M&PS...42.1529S.
doi:10.1111/j.1945-5100.2007.tb00589.x.
· · Gupta, G.; Sahijpal,
S. (2010). "Differentiation of Vesta and the parent bodies of other
achondrites". J. Geophys. Res. (Planets) 115 (E8):
E08001. Bibcode:2010JGRE..11508001G.
doi:10.1029/2009JE003525.
· · Scott W. Benson
(November 8, 2007). "Solar
Power for Outer Planets Study" (PDF). NASA. Retrieved November
27, 2014.
· · "Dawn: Mission
description". UCLA Space Physics Center. October 17, 2006. Retrieved September
28, 2007.
· · Watanabe, Susan
(July 5, 2007). "Dawn:
Spacecraft & Instruments". NASA. Retrieved August 10, 2006.
· · "Send
Your Name to the Asteroid Belt". JPL.NASA.gov. November 4, 2006.
Archived from the
original on April 11, 2007. Retrieved June 21, 2007.
· · Sierks,
et al. – The Dawn Framing Camera: A Telescope En Route to the Asteroid Belt
- MPS/DLR/IDA
· · Sierks, H.; Keller,
H. U.; Jaumann, R.; Michalik, H.; Behnke, T.; Bubenhagen, F.; BÃŧttner, I.;
Carsenty, U. et al. (2011). "The Dawn Framing Camera". Space
Science Reviews 163 (1-4): 263–327. Bibcode:2011SSRv..tmp...20S.
doi:10.1007/s11214-011-9745-4.
· · Sanctis, M. C.;
Coradini, A.; Ammannito, E.; Filacchione, G.; Capria, M. T.; Fonte, S.; Magni,
G.; Barbis, A. et al. (2010). "The VIR Spectrometer". Space
Science Reviews 163 (1-4): 329–369. Bibcode:2010SSRv..tmp..103D.
doi:10.1007/s11214-010-9668-5.
· · Righter, Kevin;
Drake, Michael J. (1997). "A magma ocean on Vesta: Core formation and
petrogenesis of eucrites and diogenites". Meteoritics & Planetary
Science 32 (6): 929–944. Bibcode:1997M&PS...32..929R.
doi:10.1111/j.1945-5100.1997.tb01582.x.
· · Drake, Michael J.
(2001). "The eucrite/Vesta story". Meteoritics & Planetary
Science 36 (4): 501–513. Bibcode:2001M&PS...36..501D.
doi:10.1111/j.1945-5100.2001.tb01892.x.
· · Prettyman, Thomas H.
(2004). "Proceedings of SPIE—Mapping the elemental composition of Ceres
and Vesta: Dawn's gamma ray and neutron detector". Instruments,
Science, and Methods for Geospace and Planetary Remote Sensing 5660:
107. doi:10.1117/12.578551.
· · Prettyman, T.H.
(August 2003). "Gamma-ray and neutron spectrometer for the Dawn mission to
1 Ceres and 4 Vesta". IEEE Transactions 50 (4): 1190–1197. Bibcode:2003ITNS...50.1190P.
doi:10.1109/TNS.2003.815156.
· · Oberg, James
(September 27, 2007). "Spacecraft’s
ion drive gets its day in the sun". MSNBC. Retrieved January 7, 2012.
· · "Dawn at Astrotech's
Payload Processing Facility". Space and Astronautics News. April 11,
2007. Retrieved June 28, 2013.
· · "Launch
of Dawn asteroid mission postponed again". New Scientist. 2007.
Retrieved June 28, 2013.
· · "NASA
Mission to Asteroid Belt Rescheduled for September Launch". NASA. July
7, 2007. Retrieved November 9, 2013.
· · Russell,
Christopher; Raymond, Carol (eds.). The Dawn
Mission to Minor Planets 4 Vesta and 1 Ceres. New York: Springer
Science+Business Media. ISBN 978-1-4614-4903-4. Retrieved August
7, 2014.
· · "ULA—One
Team for Assured Access to Space" (PDF). ulalaunch.com. Archived from the
original on September 28, 2007. Retrieved November 9, 2013.
· · Rayman, Marc D. "Dawn
Journal: Aiming away from a bull's eye at Mars". The Planetary
Society. Archived from the
original on July 16, 2011. Retrieved November 9, 2013.
· · Malik, Tariq
(February 18, 2009). "Asteroid-Bound
Probe Zooms Past Mars". Space.com. Retrieved November 9, 2013.
· · "Dawn
Receives Gravity Assist from Mars". NASA/JPL. February 28, 2009.
Retrieved January 3, 2015.
· · "NASA's
Dawn Captures First Image of Nearing Asteroid". NASA. May 11, 2011.
Retrieved September 1, 2012.
· · "NASA'S
Dawn Spacecraft Begins Science Orbits Of Vesta". NASA. August 1, 2011.
Retrieved August 7, 2014.
· · "View of Vesta from
Dawn". NASA/JPL MYSTIC simulator (updated periodically). Retrieved
September 1, 2012.
· · Wall, Mike (July 16,
2011). "NASA
Spacecraft Now Orbiting Huge Asteroid Vesta ... Hopefully". Space.com.
Retrieved July 17, 2011.
· · Amos, Jonathan (July
17, 2011). "Dawn
probe orbits asteroid Vesta". BBC. Retrieved January 22, 2015.
· · Vega, Priscilla;
Brown, Dwayne (July 16, 2011). "NASA's
Dawn Spacecraft Enters Orbit Around Asteroid Vesta". NASA. Retrieved July
17, 2011.
· · Russell, C. T. et.
al.; Raymond, C. A.; Coradini, A.; McSween, H. Y.; Zuber, M. T.; Nathues,
A.; De Sanctis, M. C.; Jaumann, R.; Konopliv, A. S.; Preusker, F.; Asmar, S.
W.; Park, R. S.; Gaskell, R.; Keller, H. U.; Mottola, S.; Roatsch, T.; Scully,
J. E. C.; Smith, D. E.; Tricarico, P.; Toplis, M. J.; Christensen, U. R.;
Feldman, W. C.; Lawrence, D. J.; McCoy, T. J.; Prettyman, T. H.; Reedy, R. C.;
Sykes, M. E.; Titus, T. N. (May 11, 2012). "Dawn at Vesta:
Testing the Protoplanetary Paradigm". Science 336 (6082): 684–686. doi:10.1126/science.1219381.
Retrieved August 7, 2014.
· · The Dawn Mission
to Vesta and Ceres. Space Science Reviews, Volume 163,
Numbers 1-4 (2011), 3-23, DOI: 10.1007/s11214-011-9836-2, via SpringerLink.
Retrieved September 11, 2012.
· · "2011:
The Dawn of Vesta Science" (PDF). Spacegrant.org. September 2011.
Retrieved November 9, 2013.
· · "Incredible
video 'fly-over' by Nasa's Dawn probe reveals huge rippled asteroid Vesta is
more like a small planet". Daily Mail.
May 15, 2012. Retrieved May 23, 2012.
· · Reddy, Vishnu; Le
Corre, Lucille; o’Brien, David P.; Nathues, Andreas; Cloutis, Edward A.; Durda,
Daniel D.; Bottke, William F.; Bhatt, Megha U.; Nesvorny, David; Buczkowski,
Debra; Scully, Jennifer E.C.; Palmer, Elizabeth M.; Sierks, Holger; Mann, Paul
J.; Becker, Kris J.; Beck, Andrew W.; Mittlefehldt, David; Li, Jian-Yang;
Gaskell, Robert; Russell, Christopher T.; Gaffey, Michael J.; McSween, Harry
Y.; McCord, Thomas B.; Combe, Jean-Philippe; Blewett, David (November–December
2012). "Delivery
of dark material to Vesta via carbonaceous chondritic impacts". Icarus 221 (2): 544–559. Bibcode:2012Icar..221..544R.
doi:10.1016/j.icarus.2012.08.011.
Retrieved August 7, 2014.
· · McCord, T. B., et.
al.; Li, J.-Y.; Combe, J.-P.; McSween, H. Y.; Jaumann, R.; Reddy, V.; Tosi,
F.; Williams, D. A.; Blewett, D. T.; Turrini, D.; Palomba, E.; Pieters, C. M.;
De Sanctis, M. C.; Ammannito, E.; Capria, M. T.; Le Corre, L.; Longobardo, A.;
Nathues, A.; Mittlefehldt, D. W.; SchrÃļder, S. E.; Hiesinger, H.; Beck, A. W.;
Capaccioni, F.; Carsenty, U.; Keller, H. U.; Denevi, B. W.; Sunshine, J. M.;
Raymond, C. A.; Russell, C. T. (November 1, 2012). "Dark
material on Vesta from the infall of carbonaceous volatile-rich material".
Nature 491 (7422): 83–86. doi:10.1038/nature11561. PMID 23128228. Retrieved August
7, 2014.
· · "NASA's
Dawn Spacecraft Probes Proto-Planet Vesta, Discovers Deposits that Give
Scientists Insight into the Origins of the Solar System". Latino
Post. October 31, 2012. Retrieved November 28, 2012.
· · Scully, J. E. C. et.al.
(2014). "Sub-Curvilinear
Gullies Interpreted As Evidence For Transient Water Flow On Vesta". 45th
Lunar and Planetary Science Conference. Universities Space Research
Association. Retrieved August 7, 2014.
· · "Dawn probe
spies possible water-cut gullies on Vesta". BBC. December 6, 2012.
Retrieved December 8, 2012.
· · "Dawn
departs Vesta to become first asteroid hopper". New
Scientist. September 6, 2012. Retrieved November 9, 2013.
· · Staff, Space.com. "NASA's
Dawn Spacecraft Says Goodbye to Giant Asteroid Vesta". Yahoo.com.
Retrieved September 6, 2012.
· · Williams, D. A.;
Yingst, R. A.; Garry, W. B. (December 2014). "Introduction: The geologic
mapping of Vesta". Icarus 244: 1–12. doi:10.1016/j.icarus.2014.03.001.
edit
· · Scully, J. E. C.;
Yin, A.; Russell, C. T.; Buczkowski, D. L.; Williams, D. A.; Blewett, D. T.;
Ruesch, O.; Hiesinger, H.; Le Corre, L.; Mercer, C.; Yingst, R. A.; Garry, W.
B.; Jaumann, R.; Roatsch, T.; Preusker, F.; Gaskell, R. W.; SchrÃļder, S. E.;
Ammannito, E.; Pieters, C. M.; Raymond, C. A. (December 2014).
"Geomorphology and structural geology of Saturnalia Fossae and adjacent
structures in the northern hemisphere of Vesta". Icarus 244:
23–40. doi:10.1016/j.icarus.2014.01.013.
edit
· · Schäfer, M.;
Nathues, A.; Williams, D. A.; Mittlefehldt, D. W.; Le Corre, L.; Buczkowski, D.
L.; Kneissl, T.; Thangjam, G. S.; Hoffmann, M.; Schmedemann, N.; Schäfer, T.;
Scully, J. E. C.; Li, J. Y.; Reddy, V.; Garry, W. B.; Krohn, K.; Yingst, R. A.;
Gaskell, R. W.; Russell, C. T. (December 2014). "Imprint of the Rheasilvia
impact on Vesta – Geologic mapping of quadrangles Gegania and Lucaria". Icarus
244: 60–73. doi:10.1016/j.icarus.2014.06.026.
edit
· · Kneissl, T.;
Schmedemann, N.; Reddy, V.; Williams, D. A.; Walter, S. H. G.; Neesemann, A.;
Michael, G. G.; Jaumann, R.; Krohn, K.; Preusker, F.; Roatsch, T.; Le Corre,
L.; Nathues, A.; Hoffmann, M.; Schäfer, M.; Buczkowski, D.; Garry, W. B.;
Yingst, R. A.; Mest, S. C.; Russell, C. T.; Raymond, C. A. (December 2014).
"Morphology and formation ages of mid-sized post-Rheasilvia craters –
Geology of quadrangle Tuccia, Vesta". Icarus 244: 133–157. doi:10.1016/j.icarus.2014.02.012.
edit
· · "NASA's Dawn
Fills out its Ceres Dance Card". NASA. December 3, 2013. Retrieved December
8, 2013.
· · McCord, Thomas B.; Castillo-Rogez,
Julie; Rivkin, Andy (2011). "The
Dawn Mission to Minor Planets 4 Vesta and 1 Ceres - Ceres: Its Origin,
Evolution and Structure and Dawn's Potential Contribution".
p. 63. doi:10.1007/978-1-4614-4903-4_5.
ISBN 978-1-4614-4902-7.
· · Mid-continent
Research for Education and Learning: McREL. "Dawn
Mission: Mission > Dawn Journal: November 30, 2013". nasa.gov.
