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Unmanned Spaceflight.com > Beyond.... > Telescopic Observations
Paolo
The special issue of Astronomy & Astrophysics on the first results from Herschel is now available, with hundreds of papers freely accessible!
http://www.aanda.org/index.php?option=com_...s/contents.html
dilo
Grazie Paolo! smile.gif
Paolo
according to Herschel's twitter (ESAHerschel) they will observe comet Honda-Mrkos-Pajdusakova on Aug 15/16. This small, short period comet has always fascinated me since it was to be flown by "tail first" by Sakigake. Too bad contact with the probe was lost before sad.gif
Paolo
from Herschel's twitter:

QUOTE
Quick look analysis of the Comet 45P/Honda-Mrkos-Pajdusakova observations by Herschel is revealing some wonderful data.


can't wait for publication...
Paolo
just published in Nature: Ocean-like water in the Jupiter-family comet 103P/Hartley 2
and this is ESA's release http://www.esa.int/esaSC/SEMER89U7TG_index_0.html
this is one of the most amazing solar system discoveries of 2011!
Paolo
according to tweets by Daniel Fischer (@cosmos4u), Herschel should run out of coolant in March 2013 and ESA is considering end of mission scenarios. Warm observations are not possible, so one idea is to deorbit it from L2 and crash it on the Moon to perform scientific observations.
Paolo
the story has been picked up by Spaceflight Now
Scientists could aim derelict telescope for moon impact
nprev
Exciting idea; very innovative!
Paolo
funny enough: it was also one of the possible end of mission scenarios for Chang'e 2. flying it back from L2 to impact the Moon for science
tanjent
Is the hardware actually damaged by the lack of coolant? If Herschel were placed somewhere where it could conceivably be restocked with consumables at some future time, could it be returned to service? I guess the people who don't want to crash it probably envision some Hubble-inspired scenario like that. I recall though, that the last Hubble service call had to be performed before the gyros and other components ceased to function entirely. It wasn't something that could wait 100 years.
Paolo
I see at least three reasons why this is not doable:
1. unlike the HST, Herschel was not designed to be serviceable
2. you need to use fuel to keep it into the halo orbit or to redirect it somewhere else to wait for servicing. I understand that fuel remaining is not a issue now, but it will become at a certain moment
3. orbital refuelling has been carried out until now with storable, room temperature liquids (hydrazine and water mostly). transfer of cryogenic fuels has yet to be tested, not to speak of the transfer of super-cold (less than 5K IIRC) liquid helium
Phil Stooke
Paolo said "funny enough: it was also one of the possible end of mission scenarios for Chang'e 2. flying it back from L2 to impact the Moon for science"



Strictly speaking the Toutatis flyby is not an end of mission scenario. The question is, what is the post-Toutatis trajectory? I am assuming for lack of other information that the spacecraft will not get very far from Earth and its orbit will bring it back, rather than heading off into a more distant heliocentric orbit. Is there any description of its current orbit?

Phil

Paolo
some insight on the decision to crash Herschel and the possible alternatives on this blog
http://herschellife.blogspot.es/1342197754...-end-of-helium/
I would have loved the Herschel trailblazer concept: placing Herschel at the Earth-Moon L2 point to perform tests for future farside communication satellites before crashing it to the surface. unfortunately, the option was apparently deemed too expensive
Paolo
Finally, no lunar impact http://herschel.esac.esa.int/latest_news.shtml
Phil Stooke
Too bad. I'm hungry for another point on the lunar map. Oh well - GRAIL coming up soon, presumably.

Phil

dtolman
They've announced the end of mission now that coolant has run out.

Probably a stupid question, but I'm guessing that the wavelengths being observed are too far into the infrared to allow a warm mission, ala Spitzer?
Seems like a lack of foresight (or penny pinching) to put up such a huge mirror, and not leave any instruments that could take advantage of it in an extended mission.

EDIT: and let me answer my own question:
http://isnerd.me/2013/04/04/some-more-ques...rning-herschel/

QUOTE
For a telescope operating at shorter wavelengths (about ten times longer in wavelength than visible light) a “warm mission” is feasible. This could have been done with Herschel, but it would have required that the surface of the telescope be made far more precise and smooth. That would have made it very much more expensive, leaving less money available for the rest of the spacecraft and the instruments.

Any space mission must be built within a certain budget, and it is usually best to design it to be as effective as possible for a certain wavelength range. Herschel actually covers a very wide range – from 55 to nearly 700 microns in wavelength. That’s more than a factor of ten, which is very impressive. To make a warm mission possible would have meant making the telescope good enough to work at ten times shorter wavelength, and adding a fourth instrument.

Paolo
by the way, the radiation monitors are still useable, and there was a proposal to keep them on. hope they will do it...

http://herschellife.blogspot.es/1342197754...-end-of-helium/

QUOTE
The ESA Space Weather Team is keen to maintain Herschel operational as long as possible because of the information that it provides on the radiation environment in Deep Space. Herschel will finish observing just as we reach solar maximum, so any time that it can spend after solar maximum will be a tremendous bonus, particularly if it could observe for a full solar cycle. For this, it does not matter of Herschel is in the Earth-Sun L2, the Earth-Moon L2, or in heliocentric orbit: the environment is similar and totally different to that in low-Earth orbit, where most satellites are, protected by the Earth’s magnetic field.
Paolo
some updates from Herschel's twitter account (https://twitter.com/ESAHerschel)

QUOTE
Through the night of May 13/14 Herschel's thrusters fired for over 7 hours to put it into a non-return trajectory outside the Earth's orbit.


QUOTE
@ESAHerschel will now drift away from Earth, while continuing to work on technology tests into June.


QUOTE
Where is @ESAHerschel now? At midnight it was 1862398km from Earth and moving away at a leisurely pace, now working on SPIRE tests.


QUOTE
Around 15:30UT this afternoon HIFI was finally switched off after (almost) 4 years work in space. SPIRE is the last instrument left on.


meanwhile, monitoring of solar radiation using the SREM instruments continue. particles from a flare in sunspot group 1748 were recorded the past week http://proteus.space.noa.gr/~srem/herschel...2013_P_flux.png
Paolo
Herschel observations of comet Honda-Mrkos-Pajdusakova (see post #4) have been published in arXiv today:

A Herschel Study of D/H in Water in the Jupiter-Family Comet 45P/Honda-Mrkos-Pajdusakova and Prospects for D/H Measurements with CCAT

very interesting. while most comets have D/H ratios unlike that of water in the Earth's oceans, comet HMP and Hartley 2 have Earth-like ratios
TheAnt
Herschel detect comet belt around Fomalhaut C

Royal Astronomical Society
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