Dawn headed to its Final Orbit around the World Ceres

[lpetrich]

NASA Jet Propulsion Laboratory Blog | Dear Isaac Newdawn, Charles Dawnwin, Albert Einsdawn and all other science enthusiasts The Dawn spacecraft has been at Ceres for over 3 (Earth) years, and it has been in space for nearly 11 years. On its way to Ceres, it orbited the asteroid Vesta from mid-2011 to mid-2012.

But its mission will likely come to an end before the end of this year. All four of the spacecraft's reaction wheels have failed. It had earlier used these wheels to change direction, and now it uses its supply of hydrazine. That is expected to run out by the end of this year and make Dawn unusable.

In its first half year at Ceres, Dawn spiraled into closer and closer nearly-circular orbits, reaching an altitude of 375 km. That is less than the asteroid's radius, 476 km. Its primary mission was done in that first half year, and after a year and a half at Ceres, Dawn started spiraling out in farther and farther orbits. It was recently in an orbit with altitudes 13,830 to 52,800 km, and it is now spiraling in again. It should reach an orbit with 350 km to 4700 km, from measuring an illustration image file, and it should then go to an orbit 35 to 2,500 km, an orbit that will be its final one.

It may be hard for Dawn to take pictures at its closest distance, but another experiment will also be active: GRaND, the Gamma Ray and Neutron Detector. It looks for these particles from the surface of the asteroid, and it has done so for most of the mission. Going close will mean that it will see those particles for small bits of the surface.

The spacecraft will be sent to very near the Occator crater, the one with the bright spots in it, to try to get an idea of those spots' composition.

 

[lpetrich]

Dawn | NASA
Dawn Mission | Dawn Home Page at JPL


Dawn Mission: Mission > Dawn Journal by Mark Rayman, Chief Engineer and Mission Director. He has been making lots of dopey Dawn puns, but then again, I find puns very punny.


2006: Dear Dawnophile, Dear Dawnologists, Dear Dawnthusiasts, Dear Dawntellectuals, Dear Dawnvironments, Dear Dawnnewyears,

2007: Dear DawNRLs, Dear Dawnthecoasts, Dear Dawngineers, Dear Dawntelligentsia, Dear Dawnventurers, Dear Countdawns, Dear Dawnpours, Dear Dawntothegrounds, Dear Dawnbassadors, Dear Dawntastics, Dear Countdawns, Dear Dawnitsways, Dear Xedawnions, Dear Extraordawnaires, Dear Dawnocentrics, Dear Aficidawnados,

2008: Dear Dawnnoisseurs, Dear Phildawnthropists, Dear Heliodawns, Dear Dawnocrats, Republidawns, and Indawnpendents, Dear Pseudawnyms, Dear Dawnlettantes, Dear Dawnminants, Dear Dawnivores, Dear Dawnniversaries, Dear Presidawntial Candidawnts, Dear Indawnviduals, Dear Dawncember30ths,

2009: Dear Dawncers, Dear Charles Dawnwins, Dear Dawnlight Saving Times, Dear Dawntpanics, Dear Dawngrades, Dear Astrodawns, Dear Dawnterested Readers, Dear Indawnfatigables, Dear Indawnmitables, Dear Dawnniversaries, Dear Dawn-o'-lanterns, Dear Dawnticlimaxes, Dear Dawnters and Sons,

2010: Plausible Dawniabilities, Dear Dawnthropoids, Dear Dawnthorities, Dear Adawnherents, Dear Multitudawnous Readers, Dear Daw9.0s, Dear Dawn Days of Summers, Dear Papardawnzzi, Dear Dawnniversaries, Dear Dawnoweens, Dear Dawnizens of the Solar System, Dear Dawnscriminating Readers,

2011: Dear Providawntial Readers, Dear Pleasant Dawnversions, Dear Conndawnsseurs, Dear Dawntalizingly Close Readers, Dear Dependawnble Readers, Dear Dawnstinations, Dear Residawnts of Vesta, Dear Dawncredibles, Dear Magdawnificents, Dear Dawnniversaries, Dear Dawnderfuls, Dear Dawnward Spirals, Dear Indawnstructibles,

2012: Dear Asdawnished Readers, Dear Ups and Dawns, Dear Dawnscoverers, Dear Dawnright Spectacular Readers, Dear Readers of all Dawnominations, Dear Upside Dawn Readers, Dear Dawnpartures, Dear Marvestalous Readers, Dear Dawnniversaries, Dear Indawnspensable Readers, Dear Dawndroids, Dear Auld Dawn Synes,

2013: Dear Dawn't Look Backs, Dear Impordawnt Readers, Dear Indawnstrious Readers, Dear Dawnscerning Readers, Dear Confidawnts, Dear Dawnamic Readers, Dear Megalodawniacs, Dear Antecedawnts, Dear Dawnniversaries, Dear All Hallows' Dawns, Dear Hand-Me-Dawns, Dear Clairvoydawnts,

2014: Dear Rendawnvous, Dear Ardawnt Readers, Dear Correspondawnts, Dear Compedawnt Readers, Dear Dawnosaurs, Dear Mastodawns, Dear Studawnts and Teachers, Dear Omnipodawnt Readers, Dear Dawnniversaries, Dear Dawnomalies, Dear Unidawntified Flying Objects, Pardawn Me, Dear Readers,

2015: Dear Abundawnt Readers, Dear Fine and Dawndy Readers, Dear Unprecedawnted Readers, Dear Dawnticipating Explorers, Let’s Get Dawn to Business, Dear Readers, Dear Emboldawned Readers, Dear Evidawnce-Based Readers, Dear Descendawnts, Dear Unhesidawntingly Enthusiastic Readers, Dear Dawnniversaries, Dear Exuldawnt Readers, Dear Superintendawnts and Assisdawnts, Dear Transcendawnts,

2016: Dear Spellbindawngs, Dear Indawnbitably Successful Readers, Dear Resplendawnt Readers, Dear Glutdawnous Readers, Dear Phodawngraphers, Dear Exdawnsions, Dear Sedawntary Readers, Dear Dawnniversaries, Dear Dawnald Trump, Hillary Clindawn and all other readers, Dear Dawnimations, Dear Decadawnt Readers, Dear Dawnimations,

2017: Dear Prodawns, Neudawns and Elecdawns, Dear Pedawntic Readers, Dear Leonardo dawn Vinci, Micheldawngelo and Other Artistic Readers, Dear Dawnonymous and Idawntified Readers, Dawn't Be Despondawnt, Dear Readers, Dear Adawnlescents, Dear Dawnniversaries, Dear Frankendawns, Skeledawns, and all other Dawn-or-Treaters, Dear Long Disdawnce Travelers,

2018: Dear Vernal Dawnquinoxes, Dear Isaac Newdawn, Charles Dawnwin, Albert Einsdawn and all other science enthusiasts,

Up to April 29

 

[lpetrich]

2018: May 31 - August 22
Dear Expecdawnt Readers, Dear Phendawnmenal Readers, Dear Dawnouements, Dear Sinceres Readers,

Interesting change, from "Dawn" names to a "Ceres" one.

 

[bilby]

2018: May 31 - August 22
Dear Expecdawnt Readers, Dear Phendawnmenal Readers, Dear Dawnouements, Dear Sinceres Readers,

Interesting change, from "Dawn" names to a "Ceres" one.

It does seem strange that he didn't continue the established ceres for adawning his salutations.

 

[lpetrich]

Marc Rayman describes the expected last moments for Dawn as an active spacecraft. The end will happen when it runs out of hydrazine, what it uses to keep properly oriented. When it runs out, it can no longer keep its solar panels facing the Sun and its main antenna pointed at the Earth, and its batteries will get drained. But it will still orbit Ceres for some decades at least.
NASA Jet Propulsion Laboratory Blog | Dear Dawnouements, (Aug 21)
NASA Jet Propulsion Laboratory Blog | Dear Sinceres Readers, (Aug 22)
These articles also contain some closeup pictures that Dawn has taken, like of the white spots in Occator crater.

Dawn Mission | News | Legacy of NASA's Dawn, Near the End of its Mission (Sep 7)

NASA Jet Propulsion Laboratory Blog | The Giant Asteroid: A Retrospective (2013 Jan 30) -- about Vesta.

Dawn is the only spacecraft to have visited two worlds in succession, going into orbit around Vesta, then departing from Vesta and going into orbit around Ceres.

Vesta had gotten hot enough to melt very early in the Solar System's history, though it has had little or no geological activity afterward. Fragments of Vesta sometimes arrive here as meteorites, an identification confirmed by Dawn's spectroscopic equipment.

Ceres, however, is composed of water-soaked rock, with some salty water in it. Some of that salt was left behind as bright spots when some of that water came to the surface and evaporated. Sort of halfway between the rocky inner planets and the icy outer moons.