Hartley 2 passed through perihelion 3 days ago, and had its nearest approach to Earth on October 20, so amateur astronomers are producing amazing views of it right now. Here's just one awesome photo; Daniel Fischer posted a blog entry today full of links to this one and many more, and I suspect his blog and Twitter feed will be full of more beautiful Earth-based pictures of Hartley 2 all week.
Comet 103P/Hartley 2
This view of comet 103P/Hartley 2, with its blue coma and red tail, was captured using a "Global Rent A Scope" instrument based in New Mexico three days after the comet's perihelion and three days before the Deep Impact spacecraft flyby.
Here's the most recent view of Hartley 2 that's available from the Deep Impact website, but it's a week old -- I suspect they'll post a new one today or definitely tomorrow, and it'll be much more impressive. This photo does not enlarge; the Deep Impact team is preferring highly frequent images to large images so that they can monitor the outbursts of material from the comet. They save only the middle 256-pixel-square area of each image from their camera, saving space for more photos; it's quite enough area to reveal the coma's structure and dynamics.
NASA / JPL-Caltech / UMD
Hartley 2 from Deep Impact, October 23
Deep Impact took this photo of Hartley 2 on October 23, 2010, 11 days before its flyby of the comet. There is now a clear fuzz of coma and tail. The comet was 13 million kilometers from the spacecraft.
The Deep Impact science team is gathered now at JPL, watching all the latest images and spectra come in. Check out the mission blog (which unfortunately does not have an RSS feed, but new posts are mentioned on Twitter) for daily updates and snapshots of the team in "action" (I put "action" in quotes because the action mostly consists of staring at computer screens -- but honestly it is very exciting seeing the team gathered together, watching new data stream in!)
To help you visualize what's going on, I highly recommend checking out JPL's new Eyes on the Solar System website, which is a really thrilling 4D simulation of pretty much everything that's going on, about to go on, or has already happened in robotic space exploration (at least that part of robotic space exploration for which the programmers at JPL could get their hands on detailed trajectory information). It is tremendously fun to use Eyes on the Solar System to follow along with the Voyagers and Pioneers, but today I'll recommend you bring up the "Destination" menu at left, select Deep Impact at Hartley 2 or Tempel 1, and spin time back and forth to see the encounters.
Twelve radar images of the nucleus of comet Hartley 2 were obtained by the Arecibo Observatory's planetary radar from October 25 to 27, 2010. This was just a week after its closest approach to Earth on October 20. Its nucleus is highly elongated and about 2.2 kilometers long, and it rotates around itself about once every 18 hours. The radar images also revealed the size, speed and direction of particles being blown off the comet.