Emily LakdawallaJan 30, 2006

Where is New Horizons now?

It's in space, of course, and has a very, very long way to go to Pluto (nearly 50 billion kilometers). But it's finally more than 1 Astronomical Unit from the Sun. I got an email from Alan Stern over the weekend with some more good news. The first Trajectory Correction Maneuver (TCM) -- a warmup for the bigger one -- was successful on Saturday. They should be gearing up for their bigger one right about now.

New Horizons performed its first trajectory correction maneuver, TCM-1A, at 1900 UTC today [Saturday]. This was a 5 meter per second calibration burn and validation burn of our propulsion system and delta-V thrusters in preparation for the somewhat larger (12 m/s) TCM-1B maneuver set for 1900 UTC on Monday.

Together these two maneuvers (1A and 1B) will refine our Jupiter aim point substantially to allow us to accurately hit the Jupiter Gravity Assist aim point for Pluto and our desired 14 July 2015 arrival date.

TCM-2 is planned for February 15. Given the early calibration numbers from TCM-1A, we estimate this maneuver will be a clean up/tweak of about 1-2 m/s; a more refined estimate for TCM-2 will be available after a couple of weeks of DSN tracking.

EDIT: A slightly later note from Stern indicates that TCM-1B was also successful, and "we're on our way to the Pluto aim point!" He added: "By the way, the mission design team believe TCM-1B, at 13.3 m/s, is likely the biggest TCM we will execute until we are at Pluto. Amazing." I agree, amazing. Well done, everybody!!

A number of people wrote to me after last week's update, asking why on Earth they are slowing down New Horizons by 18 meters per second when they worked so hard at getting lots of speed in order to minimize the incredibly long travel time to Pluto. In brief, it's because of the Jupiter gravity assist. They need Jupiter's gravity to accelerate them to Pluto -- it's like having another booster rocket on the spacecraft. To maximize the effectiveness of the Jupiter gravity assist, they have to hit an "aim point" at a very precise distance from Jupiter. A small error in hitting that aim point would change their speed not enough or too much so that they don't meet Pluto at the right place in its orbit 9 years from now. So even though it seems like they'd want that 18 meters per second, it is more important to hit that Jupiter aim point exactly, to get the right direction and speed of boost from the Jupiter gravity assist. Alan Stern told me that the launch "gave us a little overspeed. To hit the Jupiter aim point, we need to get back on the design course, which for an overspeed means slowing down."

Finally, to all of those who asked me "where is New Horizons now?", you can finally get your answer on APL's New Horizons website. Enjoy -- and be patient! There will be a lot of changes in all of our lives between now and New Horizons' arrival at Pluto. If you have any visions for what might change between now and then, enter your ideas in the New Horizons Digital Time Capsule contest. (But please don't enter photos of yourselves, your kids, your pets, etc. Yes, it's true, all of us will look different in 9 years, and your kids will have grown a lot. But try to think beyond your own family to what will change that will have an impact on whole communities, cities, countries, or the whole world.)

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