NASA's Mission to Pluto and the Kuiper Belt
As August begins, the New Horizons spacecraft continues its space-simulation testing in a large vacuum chamber at NASA's Goddard Space Flight Center. The chamber we are using is capable of achieving a vacuum of about one-billionth of an atmosphere and running the spacecraft at any temperature it could conceivably see on its journey from Earth to Pluto. In a real sense, our spacecraft is now "at home"for the first time - in a close facsimile of the space environment that she was built to operate in.
While New Horizons is in test at Goddard's vacuum chamber, our engineering and operations teams have been running mission simulations, thermal performance tests, and various special tests on "the bird."Many of the tests are run at both hot and cold temperatures. In addition to testing the spacecraft subsystems, all seven of the scientific instruments aboard the spacecraft are being put through their paces. To make the testing as realistic as possible, almost every test operation is run just as it would be in flight - from the Space Science Mission Operations Center back at the Johns Hopkins University Applied Physics Lab (APL).
The testing has been going well. We have gained a great deal of experience with the spacecraft, showing it operates almost exactly as expected. The teams have worked out many of the bugs in the initial drafts of our flight procedures.
In a system as complex as a spacecraft, finding hardware and software problems during ground testing is commonplace. Last month, spacecraft testing revealed a hardware problem in one of the 64-gigabit Solid State Recorders aboard New Horizons. These flash memory devices, called SSRs, are the memory banks on which the spacecraft stores all of the scientific and engineering data it generates. For redundancy purposes, New Horizons carries two SSRs, and we require that both be operational at launch. The problem with our sick SSR is probably related to a manufacturing defect on a single circuit card, and is not expected to be hard to repair. The sick SSR will have to be removed from the spacecraft and repaired after New Horizons emerges from the vacuum chamber in September. The repaired device must be successfully tested on its own and on New Horizons before it can be certified as flight ready.
Although one would like a spacecraft that is completely free of problems from the minute it is put together, I'm very glad we found the SSR problem, since it could not be fixed after launch. Indeed, this is why we do the testing we are doing - to smoke out design, fabrication, software, and procedural problems before we get into flight.