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Forum:Satellites - Robotic Probes
Topic:New Horizons to Pluto: Viewing and comments
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The panel of experts included:

  • John Grunsfeld, astronaut, NASA's Associate Administrator for the Science Mission Directorate
  • Hal Weaver, Project Scientist for New Horizons
  • Jamey Szalay, David James, and Tiffany Finley, current and former members of the New Horizons Student Dust Counter instrument team
  • Gabe Rogers, New Horizons Guidance and Control Engineer
Robert PearlmanNASA released today the first color photo of Pluto and Charon, as captured by New Horizons from a distance of about 71 million miles (roughly the distance from the Sun to Venus).

The New Horizons team also today detailed when imagery will be delivered to Earth. The Planetary Society's Emily Lakdawalla has an excellent overview and schedule of imagery transmissions here.

On Sunday, July 12, New Horizons will transmit the last of its optical navigation data. These images will have lower resolution than the images we have already received from Dawn at Ceres. Then, on Sunday and Monday, July 12 and 13, there will be a series of four "Fail Safe" downlinks. These are designed to return a minimum set of data from all instruments, just in case New Horizons does not survive the flyby. A last downlink ending overnight Monday July 13, called "E-Health 1," will include one last pre-closest approach photo of Pluto.

Then there is a nail-biting 24-hour period of waiting while New Horizons concentrates on flyby science and does not communicate with Earth, followed by the much-anticipated beep of the "Phone Home" downlink on Tuesday night, July 14. Following closest approach, on Wednesday and Thursday, July 15 and 16, there will be a series of "First Look" downlinks containing a sampling of key science data. Another batch of data will arrive in the "Early High Priority" downlinks over the subsequent weekend, July 17-20. Then there will be a hiatus of 8 weeks before New Horizons turns to systematically downlinking all its data.

...for nearly two months, until September 14, New Horizons will switch to near-real-time downlinking of data from instruments that generate low data volumes (like SWAP and PEPSSI) while it transmits just housekeeping information for all of the rest of the data. No new images will arrive on the ground during this time.

On September 14, New Horizons will begin downlinking a "browse" version of the entire Pluto data set, in which all images will be lossily compressed. It will take about 10 weeks to get that data set to the ground. There will be compression artifacts, but we'll see the entire data set. Then, around November 16, New Horizons will begin to downlink the entire science data set losslessly compressed. It will take a year to complete that process.

The raw images received won't be posted to the web directly, but team members promised that imagery would be made available as fast as possible after they have had a chance to look at the data.
BlackarrowIt's a far cry from the near-instantaneous availability of images of Neptune taken by the 1970s-designed Voyager 2 in 1989.

Still, that's progress for you!

Robert PearlmanVoyager 2 and New Horizons were/are constrained by the amount of data they could/can record onboard. Voyager was equipped with a tape recorder; New Horizons has solid state memory.

For Voyager 2's encounter with Neptune, NASA coupled the Deep Space Network with the Parkes radio observatory and the 27 25-meter dishes at the NRAO's Very Large Array.

As Emily Lakdawalla describes here, New Horizons' signal can only be detected by the DSN's 70-meter dishes, but can cache much more data than Voyager to transmit over time. As such... takes 42 minutes to return one LORRI photo to Earth. Most communications sessions last about eight hours. That's eleven images per communications session. And that assumes that New Horizons is transmitting only LORRI data, which it's not; there are other science instruments and spacecraft housekeeping data, too. The Deep Space Network has only three 70-meter dishes, and there is a lot of competition for time on them; New Horizons is lucky to get one communications session per day. And while New Horizons is pointing its dish at Earth, it can't point at anything else, including Pluto. It has to choose between communicating and taking data.
BlackarrowI stand by what I previously posted. 26 years ago I attended a special event at Armagh Planetarium and watched a stream of incredible images coming through from Neptune. In 2015 I was going to take a day off work to watch a stream of images from Pluto via CNN, Sky News, BBC and NASA TV. Clearly, I would be wasting my time.

I wonder whether we will see the best New Horizon images before or after we see close-ups of Ceres...or after we FINALLY see fully-enhanced Philae landing-site images.

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