Exploring Asteroid Belt Dawn Spacecraft Exploring Asteroid Belt

DAWN SPACECRAFT First Mission to Orbit 2 Asteroids Use of Ion Propulsion

Launch on Delta III Early September 4 Year Mission to the Asteroid Belt

http://pds.jpl.nasa.gov/planets/welcome.htm

Ceres Vesta Exploring Meteorite mysteries.pdf http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Meteoroids.to.Meteorites/Exploring.Meteorite.Mysteries/.index.html

Asteroid Sizes Exploring Meteorite mysteries.pdf http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Meteoroids.to.Meteorites/Exploring.Meteorite.Mysteries/.index.html http://www.jpl.nasa.gov/releases/2000/kleopatra.html http://neo.jpl.nasa.gov/images/ida.html http://neo.jpl.nasa.gov/images/gaspra.html

LINEAR NEO Search Systems http://impact.arc.nasa.gov/

Asteroids: Years of Discovery Exploring Meteorite mysteries.pdf http://spacelink.nasa.gov/Instructional.Materials/Curriculum.Support/Space.Science/Meteoroids.to.Meteorites/Exploring.Meteorite.Mysteries/.index.html

Hubble! http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001066.html GRIN NASA Center: Johnson Space Center Image # : STS082-709-097 Date : 02/19/1997 Hubble Redeployment Full Description Attached to the "robot arm" the Hubble Space Telescope is unberthed and lifted up into the sunlight during this the second servicing mission designated HST SM-02. Keywords STS-82 Discovery Payload Bay Hubble Space Telescope HST Remote Manipulator System RMS Canada Arm Subject Category Space Shuttle, Hubble, Reference Numbers Center: JSC Center Number: STS082-709-097 GRIN DataBase Number: GPN-2000-001066

http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000672.jpg GRIN NASA Center: Kennedy Space Center Image # : 89PC-0732 Date : 8/3/1989 Galileo Preparations Full Description In the Vertical Processing Facility (VPF), the spacecraft Galileo is prepared for mating with the Inertial Upper Stage booster. Galileo will be launched aboard the Orbiter Atlantis on Space Shuttle mission STS-34, October 12, 1989 and sent to the planet Jupiter, a journey which will take more than six years to complete. Keywords Galileo STS-34 Atlantis Vertical Processing Facility VPF Subject Category Planet-Jupiter, Voyager-Galileo, Reference Numbers Center: KSC Center Number: 89PC-0732 GRIN DataBase Number: GPN-2000-000672 Source Information Creator/Photographer: NASA Original Source: DIGITAL

http://neo.jpl.nasa.gov/images/composite.jpg http://neo.jpl.nasa.gov/images/gaspra.html These are views of the three asteroids that have been imaged at close range by spacecraft. The image of Mathilde (left) was taken by the NEAR spacecraft on June 27, 1997. Images of the asteroids Gaspra (middle) and Ida (right) were taken by the Galileo spacecraft in 1991 and 1993, respectively. All three objects are presented at the same scale. The visible part of Mathilde is 59 km wide x 47 km high (37 x 29 miles). Mathilde has more large craters than the other two asteroids. The relative brightness has been made similar for easy viewing; Mathilde is actually much darker than either Ida or Gaspra.

http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1996-008A NEAR Shoemaker NSSDC ID:1996-008A Other Name(s) Near Earth Asteroid Rendezvous NEAR 23784 -------------------------------------------------------------------------------- Launch Date/Time: 1996-02-17 at 20:43:27 UTC On-orbit dry mass: 487 kg Nominal Power Output: 1800 W Description The Near Earth Asteroid Rendezvous - Shoemaker (NEAR Shoemaker), recently renamed in honor of Gene Shoemaker, is designed to study the near Earth asteroid Eros from close orbit over a period of a year. The primary scientific objectives of NEAR are to return data on the bulk properties, composition, mineralogy, morphology, internal mass distribution and magnetic field of Eros. Secondary objectives include studies of regolith properties, interactions with the solar wind, possible current activity as indicated by dust or gas, and the asteroid spin state. This data will be used to help understand the characteristics of asteroids in general, their relationship to meteorites and comets, and the conditions in the early solar system. To accomplish these goals, the spacecraft is equipped with an X-ray/gamma ray spectrometer, a near infrared imaging spectrograph, a multi-spectral camera fitted with a CCD imaging detector, a laser rangefinder, and a magnetometer. A radio science experiment will also be performed using the NEAR tracking system to estimate the gravity field of the asteroid. The total mass of the instruments is 56 kg, and they require 81 W power. Mission Profile The ultimate goal of the mission is to study the near Earth asteroid 433 Eros from orbit for approximately one year. Eros is an S-class asteroid approximately 13 x 13 x 33 km in size, the second largest near-Earth asteroid. Initially the orbit will was circular with a radius of 200 km. The radius of the orbit was brought down in stages to a 50 x 50 km orbit on 30 April 2000 and decreased to 35 x 35 km on 14 July 2000. The orbit was raised over succeeding months to a 200 x 200 km orbit and then slowly decreased and altered to a 35 x 35 km retrograde orbit on 13 December 2000. The mission will end with a touchdown in the "saddle" region of Eros on 12 February 2001. After launch on a Delta 7925-8 (a Delta II Lite launch vehicle with nine strap-on solid-rocket boosters and a Star 48 (PAM-D) third stage) and exit from Earth orbit, NEAR entered the first part of its cruise phase. It spent most of this phase in a minimal activity "hibernation" state, which ended a few days before the flyby of the 61 km diameter asteroid 253 Mathilde on June 27, 1997. The spacecraft flew within 1200 km of Mathilde at 12:56 UT at 9.93 km/sec, returning imaging and other instrument data. On July 3, 1997 NEAR executed the first major deep space maneuver, a two-part burn of the main 450 Newton thruster. This decreased the velocity by 279 m/sec and lowered perihelion from 0.99 AU to 0.95 AU. The Earth gravity assist swingby occurred on January 23, 1998 at 7:23 UT. The closest approach was 540 km, altering the orbital inclination from 0.5 to 10.2 degrees, and the aphelion distance from 2.17 to 1.77 AU, nearly matching those of Eros. Instrumentation was active at this time.

http://near.jhuapl.edu/iod/20010208/index.html NEAR Shoemaker's Path This plot shows NEAR Shoemaker's projected path from orbit to the surface of Eros on Feb. 12. Viewed from the sun, Eros is moving in a clockwise direction as it spins on its axis, while the spacecraft moves counterclockwise in a circular orbit 35 kilometers (22 miles) from the asteroid's center. The pair will be about 316 million kilometers (196 million miles) from Earth. NEAR Shoemaker will de-orbit with a short engine burn at 10:31 a.m. EST, about 4 ½ hours before it's scheduled to reach the surface. The final leg of the controlled descent begins with the spacecraft about 5 kilometers (3 miles) above Eros; it will then execute an unprecedented series of four engine burns designed to slow its descent from about 20 mph to about 5 mph. NEAR Shoemaker is expected to touch down in an area bordering Himeros, the asteroid's distinctive saddle-shaped depression, after providing the highest-resolution images ever taken of Eros' boulder-strewn, cratered terrain.

EROS Asteroid 433 http://impact.arc.nasa.gov/

http://near.jhuapl.edu/iod/20010131/index.html Closing in on Eros These four images are among thousands NEAR Shoemaker acquired during several low-altitude passes over Eros from January 25-28, 2001. From upper left to lower right, the images show Eros' bouldery surface at increasing resolution. The image at upper left was taken January 27 of a point 13.5 kilometers (8.4 miles) away; the one at the upper right was taken January 26 from 11.1 kilometers (6.9 miles) away. Each top scene is about 550 meters (1,815 feet) across. The image at bottom left was taken January 26 from 4.9 kilometers (3 miles) away, and the bottom right image was taken January 28 from a similar distance. Each lower scene is about 230 meters (760 feet) across. (Images 0155981852, 0155883236, 0155888661, 0156087736)

http://near.jhuapl.edu/

Hayabusa Visiting Asteroid Itokawa http://www.hayabusa.isas.jaxa.jp/e/index.htmlHayabusa

Hayabusa Visiting Asteroid Itokawa http://www.isas.ac.jp/e/snews/2005/1124_hayabusa.shtml Hayabusa Landed on and Took Off from Itokawa successfully Detailed Analysis Revealed Hayabusa attempted its first soft-landing on Itokawa for the purpose of touch down and sample collection on November 20-21, 2005. Below is the data information with the related advance report on its status. Hayabusa started descending at 9:00pm on Nov. 19th, 2005 (JST) from 1km in altitude. The guidance and navigation during the process of approach was operated normally, and at 4:33am on Nov. 20th, the last approach of vertical descent was commanded from ground, of which soft-landing was successfully achieved almost on the designated landing site of the surface. Deviation from the target point is now under investigation but presumed within a margin of 30m. The approaching trajectories in the quasi-inertial coordinate system and Itokawa-fixed coordinate system are shown in Data-1. Information on the altitude and its rate during the descent as measured by Doppler data is shown in Data-2. The velocity at the time of starting descent was 12cm/sec. At the altitude 54m at 5:28am, wire-cutting of target marker was commanded, after which, at 5:30am at altitude 40m, the spacecraft autonomously reduced its own speed by 9cm/sec to have substantially separated the target marker. It means that Hayabusa's speed became 3 cm/sec. Separation and freefall of the marker was confirmed from the image (Data-3) as well as from descending velocity of the spacecraft at the time of reducing the speed. The marker is presumed to have landed on southwest (upper right on the image) of MUSES Sea. Hayabusa then switched its range measurement from Laser Altimeter (LIDAR) to Laser Range Finder (LRF) at the altitude 35m and moved to hovering by reducing descending speed to zero at 25m above the surface, below where Hayabusa, at 5:40am at altitude 17m, let itself to freefall, functioning itself to the attitude control mode adjustable to the shapes of the asteroid surface. At this point, the spacecraft autonomously stopped telemetry transmission to the earth (as scheduled) to have changed to transmission with beacon mode more efficient for Doppler measurement by switching to low gain antenna (LGA) coverable larger area. Since then, checking of the onboard instruments was not possible on a real time basis (as scheduled), but as a result of analyzing the data recorded onboard and sent back to the earth in the past two days, Hayabusa seemed to have autonomously judged to abort descending and attempted emergency ascent because its Fan Beam sensors for obstacle checking detected some kind of catch-light. Allowable margin is set for Hayabusa for its attitude control, in the case the spacecraft takes off the ground by accelerating the velocity on its own. Under such circumstances, the then spacecraft's attitude was out of the margin, because of which continuing of safe descent was consequently chosen. As a result, Hayabusa did not activate its Touch Down Sensor function. At the timepoint of Nov. 21, Hayabusa was judged not to have landed on the surface. According to the replayed data, however, it was confirmed that Hayabusa stayed on Itokawa by keeping contact with the surface for about 30 minutes after having softly bounced twice before settling. This can be verified by the data history of LRF and also by attitude control record (Data-4). This phenomenon took place during switching interval from Deep Space Network (DSN) of NASA to Usuda Deep Space Center, because of which the incident was not detected by ground Doppler measurement. The descending speed at the time of bouncing twice was 10cm/sec. respectively. Serious damage to the spacecraft has not been found yet except heating sensor that may need checking in some part of its instrument. Hayabusa kept steady contacting with the surface until signaled from ground to make emergency takeoff at 6:58am (JST). The Touch Down Sensor supposed to function for sampling did not work because of the reason above stated, for which reason firing of projector was not implemented in spite of the fact that the spacecraft actually made landing. The attitude at landing is so presumed that the both bottom ends of +X axis of sampler horn and either the spacecraft or tip end of the solar panels was in contact with the surface. Hayabusa became the world-first spacecraft that took off from the asteroid. Really speaking, it is the world-first departure from an celestial body except the moon. After departure from the asteroid by ground command, Hayabusa moved into safe mode due to the unsteady communication line and the conflict with onboard controlling and computing priority. The comeback from safety mode to normal 3-axis control mode needed full two days of Nov. 21 and 22. Owing to this reason, replaying of the data recorded on 20th is still midway, which means the possibility to reveal much more new information through further analysis of the data. As of now, the detailed image of the landing site to know its exact location has not been processed yet. Hayabusa is now on the way to fly over to the position to enable landing and sampling sequence again. It's not certain yet if or not descent operation will be able to carry out from the night of Nov. 25 (JST). We will announce our schedule in the evening of Nov. 24. Descending and landing operation will all depend upon availability of DSN of NASA. We would like to express our sincere gratitude for cooperation of NASA for tracking networks including backup stations. (Data-1) Approach to Itokawa and descending trajectory Figures below indicate approaching trajectory of Hayabusa at descending and landing on Nov. 20th. Fig. 1a describes the trajectory in quasi-inertial coordinate system with z-axis (bottom of fig.) directed toward the earth. Fig. 1b describes the trajectory as against the Itokawa-fixed coordinate system. The trajectory plan was altered according to the occasion during its operation but it is clear from the figure that actual flight route was very close to the one planned in advance. Fig. 1a: Actual descending trajectory as compared to the scheduled plan. (Quasi-inertial coordinate system) Fig. 1b: Actual descending trajectory as compared to the scheduled plan. (Itokawa-fixed coordinate system) Fig. 1c is to comply with fig. 1a to show actual trajectory overlapped on alternated trajectory plan subject to changes from time to time according to the occasional situation. Each dot indicates the location of the spacecraft presumed on ground from the surface shapes by processing the compressed image data occasionally. Figures show that guidance was carried out almost according to the scheduled trajectory. Fig. 1c: Navigation and guidance (Quasi-inertial system) From further up in altitude, the dotted locations presumed from the surface shapes vary with discrepancy but from below 1km sufficiently reliable information is obtained. The figure shows that the spacecraft was precisely guided according to re-scheduled trajectory plan. (Data 2): Data history of descending altitudes to Itokawa and its descending rate. Fig. 2a is the Doppler velocity history measured at Usuda and DSN stations, which roughly indicates the descending velocity of Hayabusa to Itokawa. The figure shows that the velocity of Hayabusa at the start of vertical descent was about 12cm/sec. and that the spacecraft reduced its speed autonomously controlling the velocity accelerated by the gravity of the asteroid. Fig. 2b shows the updated altitude information at the right timing that was presumed from the surface conditions by integrating Doppler velocity information. The figure indicates the approximate altitude from the center of the asteroid mass. The dotted green line in the figure indicates the altitudes from the surface of ITOKAWA measured by laser altimeter. We can roughly understand the situation of each event at the time of happening by referring to both data of laser altimeter and Doppler velocity information. Fig. 2a: Doppler measurement during descent of Hayabusa Fig. 2b: Altitude history of Hayabusa during descent (or distance history from the center of the asteroid mass). The increase in Doppler velocity at 5:40am (JST) (21:40 world time) is because of landing on the surface of Itokawa as further explained below. From then on, tracking was switched to Usuda station, because of which we could not obtain Doppler velocity information for a while but the movement of the spacecraft was partly known from LRF, of which data has been partly analyzed as to the later movement of the spacecraft. (Data 3) Target marker with 880,000 names separated from Hayabusa and tracking from aboard. The target marker was released from the spacecraft at the relative velocity of 9cm/sec. The delivery location is southwest of (right under in fig. 3) MUSES Sea. The target marker was designed to reduce bouncing rate by appropriately filling up the inside of aluminum sphere with fine pellets made of high-polymer materials to induce multiple collisions inside to increase consumption of energy. The marker was developed through repeated tests conducted on ground as well as in a non-gravity vacuum tube to prove its low repulsion.

Dawn Trajectory

Ion Propulsion

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