Cassini

[Scorus]

Odległy przelot koło Enceladusa z 12 grudnia.

Obrazy NAC:

(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178803.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178807.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178809.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178811.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178813.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178815.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178817.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178819.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178822.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178824.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178826.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178827.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178829.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178831.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/N00178834.jpg)

Obrazy WAC:

(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/W00071006.jpg)


(http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS71/W00071007.jpg)

[gregorius]

piękne:)

[KP]

Zawsze jestem pod wrażeniem po obejrzeniu każdego podsumowania miesiąca. 

[pogrzex]

Intrygująca jest ta granica między powierzchnią silnie pokrytą kraterami, a tą dużo młodszą bez kraterów.

[kanarkusmaximus]

A tak na marginesie - czy są już jakieś konkretne plany zakończenia misji Cassini? Wiem, że zakończy się to pewnie wejściem w atmosferę Saturna, ale czy są już jakieś koncepcje tej operacji?

[Scorus]

Naturalnie, w 2017r Cassini będzie latał między atmosferą a pierścieniami po orbitach proksymalnych, a potem ulegnie deorbitacji, 15 września. Jeszcze 5.5 roku, szmat czasu, dłuższy niż misja nominalna.

The Cassini navigation team has discovered that it is possible to move
the spacecraft orbit's inner ring-plane crossing all the way over
Saturn's entire main ring system, from just beyond the F ring, to the
cleared gap between Saturn's upper atmosphere and inner portion of the
main rings, using one single Titan flyby.  So far, it has been
impossible to get very close to Saturn itself due to the presence of
the main rings out to over 140,000 km from the center of Saturn. During
SOI the spacecraft passed 18,000 km from the cloud tops, and that is
the closest the project ever expected to get to the planet and rings,
enabled by the hyperbolic approach trajectory. It was thought that
there was no feasible way to construct an orbit with reasonable period
that gets any closer to Saturn and yet does not pass through the main
rings - the implementation of which would undoubtedly destroy the
spacecraft. No safe gaps in the main ring system exist that could be
employed as intermediate steps.
 
This proximal orbit geometry is implemented by raising the orbit
inclination to a moderately high level (~63 degrees) and placing the
inner ring-plane crossing barely but safely outside the main rings. The
other ring-plane crossing is located at Titan, as usual, since Cassini
must continually encounter Titan to employ its significant gravity
assist resources. Then, with one flyby, the orbit is altered to move
the ring-plane crossing to between 2,000 to 5,000 above the 'cloud
tops' of Saturn (1 bar level). The environment is known well enough for
the project to conclude with sufficient confidence that the risk of
debris impact or atmospheric tumbling is acceptably small. Furthermore,
the radiation environment is not significantly different from that
experienced during SOI.
 
The proposed end phase includes 22 orbits in this region, called
proximal orbits.  This Juno-like mission phase offers significant
unique science opportunities for Cassini, including gravity mapping
measurements, high resolution ring observations, and in-situ
measurements of Saturn's atmosphere.
 
Final disposal of the spacecraft will take place within Saturn's
atmosphere on 15 September 2017. This entire trajectory, starting after
the last targeted proximal-injecting Titan flyby, is entirely
ballistic, requiring no further maneuvers. In other words, the end of
mission is assured regardless of the spacecraft condition. It is
anticipated that this disposal strategy will be acceptable for
Planetary Protection.

(http://starbrite.jpl.nasa.gov/pds/viewMissionProfile.jsp?MISSION_NAME=cassini-huygens)

Trzeba pamiętać, że jeszcze nic tak nie latało.

[ekoplaneta]

Szkoda kończyć Cassiniego, tym bardziej że jego pokroju sonda szybko nie powstanie 
Czy data 2017 rok związana jest może z wyczerpywaniem się paliwa oraz chęcią uniknięcia przez NASA niekontrolowanego upadku sondy na księżyce Saturna (możliwość kontaminacji tych ciał ziemskimi mikrobami?)

[Scorus]

Wiąże się to z ilością paliwa do manewrów. Alternatywą było umieszczenie sondy na odległej, stabilnej orbicie. Jednak uznano, że badania wykonane z takiej orbity będą stosunkowo ubogie i mało wartościowe. Aktualny scenariusz powala na zebranie danych na temat pola grawitacyjnego Saturn, jego atmosfery i wewnętrznej magnetosfery oraz pierścieni. A ponadto wykonanych zostanie kilka dalszych przelotów kolo Tytana. Można powiedzieć, że będzie to zupełnie nowa faza misji, realizująca cele naukowe Juno na Saturnie.