'New Horizons' may need to change trajectory

[VeeJay]

Hi,

I read this article that says that the "New Horizons" spacecraft that's set to buzz by Pluto, may have to change it's trajectory due to the possibility of debris and ejecta from Pluto's moons.

http://www.universetoday.com/98026/new- ... more-98026

But what really blew my mind was this statement:
“But we won’t pass HST resolution till we’re about 10 weeks out, in April 2015."

Wow! Seriously? Only in the last 10 weeks of a 9 year voyage can a satellite see better than Hubble?
That telescope never ceases to amaze me.

[Airconvent]

The Hubble had a large mirror and was designed optically for visual observations. The New Horizon on the other hand has to make do with much smaller optics as they need to share precious space with more important instruments. And while I am excited by its trip to the Planet Pluto (yes...planet!!) , I am also sad that after decades of planning and flight time, they are only able to do a fly past. They where rushing to meet the dateline before Pluto's atmosphere freezes (its moving further away from the Sun at the moment), so do not have time to design an orbiter nor have the money to build a craft big enough to store the fuel required for orbit insertion. So this would be a once-in-lifetime chance to see it until a few hundred years later.
I also remembered as a Primary school kid, I learnt that the furthest planet from us then was Neptune because Pluto was still inside the orbit of Neptune in its long elliptical orbit!. Imagine that! It has since moved much further out now.

[starfinder]

Yes, agree that it would have been good if NASA had designed the spacecraft to orbit Pluto, rather than merely fly by it! I didn't know the background to that before reading Airconvent's post. It seems something of a waste to go that far and only swing by Pluto in less than a day.

Speaking about optics, I recall reading this article a few months ago:
http://www.boulder.swri.edu/pkb/ssr/ssr-lorri.pdf
It's a 30-pg .pdf doc which which describes in detail the technical aspects and objectives of New Horizon's main imager (LORRI). The article was written by people at The Johns Hopkins University Applied Physics Laboratory and SSG Precision Optronics Inc, which jointly designed and built LORRI.

There are some photos of the actual OTA. Here are some extracts from the text:

"The LOng-Range Reconnaissance Imager (LORRI) is the high resolution imaging instrument for the New Horizons mission to Pluto, its giant satellite Charon, its small moons Nix and Hydra, and the Kuiper Belt... . LORRI is a narrow angle (field of view=0.29°), high resolution (4.95 μrad pixels), Ritchey-Chrétien telescope with a 20.8 cm diameter primary mirror, a focal length of 263 cm, and a three lens field-flattening assembly. A 1024 × 1024 pixel (optically active region), thinned, backside-illuminated charge-coupled device detector is used in the focal plane unit and is operated in frame transfer mode. "

"The OTA, aside from the focal plane unit and thermal blanketing, was designed and built by SSG Precision Optronics, Inc., of Wilmington, Massachusetts, USA. The primary and secondary reflecting optical elements are constructed of SiC. The telescope is a 2630 mm focal length, f/12.6 Ritchey—Chretien design. Three field-flattening fused silica lenses, located in front of the focal plane unit, are the only refractive elements in the system."

"The New Horizons mission has a long focal length, narrow angle imager for several reasons. Pluto is the smallest planet, and New Horizons flies by quickly, so the encounter science observations occur within one Earth day – but with LORRI, New Horizons will be able to image the Pluto system at higher resolution than any Earth-based telescope can (even the Hubble Space Telescope, or its successor in 2015) for 90 days prior to encounter. These images will provide an extended time base of observations, for studies of the shapes, rotations, and mutual orbits of both Pluto and Charon, and for characterizing surface changes."

"Finally, we have not yet discovered the Kuiper Belt object(s) to which New Horizons will be targeted after the Pluto-Charon encounter, and extensive Earth-based observing campaigns are searching for potential targets. However, even after discovery, the heliocentric orbits of the targets cannot be measured with sufficient accuracy from Earth to enable the New Horizons spacecraft to fly to them, unless the targets are also observed directly from the spacecraft. The direction in which the target is seen from the spacecraft is then used to steer the spacecraft to the target by optical navigation. LORRI is expected to play a key role, by making the first and highest resolution detections of the Kuiper Belt target object from New Horizons, more than 40 days before closest approach."


Wow, my humble f/10 8" (20cm) SCT has about the same aperture and focal length as the main telescope on New Horizons!

Reading the last quoted para above, I suppose one plus of New Horizons not orbiting Pluto is the possibility of imaging a Kuiper Belt Object... if they get to it. Hmmm....

As for Pluto itself, I wonder whether there would be any major surprises when New Horizons sends back the first clear images. Perhaps Pluto is unlike anything else in the Solar System seen before! Only time would tell.

[VeeJay]

So a hypothetical question - do you think we could learn more about Pluto/Charon by ramming into it?
Destructive, I know, but all for SCIENCE!