something interesting going on. That’s what determined our choice of
which side to image at closest approach. I think the findings show that
we made the right choice!’
Figure 4 (a): An example of the best pre-flyby maps of Pluto, made from images from the Hubble Space Telescope in 2002 and 2003, showing contrasts in albedo. The target hemisphere was that centred on the equator and a longitude of 180°, the location of the bright feature named Sputnik Planum after encounter. Credit:
NASA/JHUAPL/SwRI/Marc Buie
Fig 4 (b): Panchromatic composite global map of Pluto created from images taken at varying distances, and
hence, at different resolutions. Sputnik Planum is clearly visible. The dark features along the equatorial region
are also clearly resolved. Note that much of the southern hemisphere, currently tilted away from the Sun, is
not shown in this map. Credit: NASA/JHUAPL/SwRI
Early surprises – working round
Pluto’s new moons
86
86
New Horizons had a chance to try out its science instruments during
its flyby of Jupiter in early 2007, studying the giant planet’s atmosphere,
magnetosphere, moons and ring system. Even during the long cruise
phase of the mission beyond Jupiter, when the spacecraft spent much
time in hibernation mode, there was much to keep the New Horizons
team occupied. In particular, Leslie Young describes what happened
when new moons were discovered orbiting Pluto after the mission had
launched in January 2006 (see Fig. 5).
‘We got a surprise when we discovered Kerberos and Styx! We’d discovered Nix and Hydra in 2005, which was exciting, two extra targets
and we were able to configure in our arrival time and our observing
sequence to do a good job on them. When we discovered Kerberos
(June 2011) and Styx (June 2012), we thought ‘Oh my God! How much
else is out there?’ We weren’t so much worried about hitting a moon,
the odds are really small, but if you get a moon and meteorites hitting
it, they’ll knock off dust which will hang around in the system because
the moons don’t have enough gravity to hold onto it. If you hit something the size of a chick-pea, it could be a bad day for New Horizons!
So we had that period of about two years of unscheduled and nervewracking work, taking simulations with pieces of the spacecraft to
fancy gun-ranges and coming up with entire new trajectories – what
we called SHBOTs (Safe Haven by Other Trajectories) - and whole new
observing plans to make things less vulnerable.
In case of problems, there were two tricks we could use. One was to
www.RocketSTEM .org