May 12, 2008

Hubble Guidance device can avoid Skylab encore

Author: Shelby G. Spires; Time Aerospace Writer Edition: 2
Section: Local News
Page: 1A

Even though the simple piece of aluminum had boxes painted in black and white shapes, it wasn't a piece of 1960s pop art that Joel Burcham was holding at the Advanced Optical Systems Inc. lab recently. "It does sort of look like a crazy, conceptual art piece," Burcham, an AOS senior scientist, said with a laugh. "It'll be used in an artful way, I guess." Looking like a squat Christmas tree, it is part of an Advanced Video Guidance Sensor. Similar devices will take a ride on the space shuttle to be placed on the Hubble Space Telescope during this fall's final Hubble servicing mission. Black-and-white blocks, used as targets, help a spacecraft (with or without a crew) dock with Hubble by using a video camera.

It's part of an AOS technology that has been used on space shuttle missions and satellite probes for over the past decade. "Even though Hubble is going to be upgraded, and have its life extended, one day it will have to come down," said AOS Chairman and CEO Richard Hartman. "NASA is probably not going to launch a recovery mission for it. "So, Hubble will have to be safely brought down to Earth. This equipment will allow (another satellite) to dock with it and bring it down." Debris from space vehicles has been a concern for decades. In July 1979, NASA managers were forced to watch helplessly as the space station Skylab's orbit degraded to a point where it came crashing back to Earth over Australia and much of the South Pacific. "This is intended to avoid the same event that happened to Skylab. NASA doesn't want to have to de-orbit Hubble and it land in a populated area or even threaten a populated area," said Fred D. Roe, AOS vice president and principal engineer.

A computer box will also be installed on Hubble that contains AOS's ULTOR software - an advanced program that facilitates the docking, Hartman said. Other docking technologies exist. The Russians have been using radio beams to dock unmanned Progress spacecraft with space stations for decades. Lasers could also be used, but "video guidance has the really big advantage of being less complicated and inexpensive," said Joel Hannah, AOS electrical and software engineering manager. "You can use a video camera from right off the shelf for this. You really can't be less complicated than that." NASA and the Department of Defense have used the video guidance system with success in the past. In addition to two shuttle missions, it was used during the 2005 Demonstration of Autonomous Rendezvous Technology (DART) mission to "fly" two satellites in proximity with each other. "Even though that part of the mission was not successful," said Keith Farr, AOS president, "our equipment performed well." In 2007, the guidance system was used on the Pentagon-managed Orbital Express mission, which docked two satellites.

The video guidance system also is being developed for NASA's next spacecraft - the Orion crew capsule - which will be used to loft astronauts to the International Space Station or the moon. Guidance targets, similar to ones headed for Hubble, will be placed on objects with which the Orion will have to dock. Missions in the planning stage now call for the advanced Apollo-like capsule to dock with rocket stages, lunar landers and the space station. Targets are already in place on the space station. "Really, it'll be able to dock with whatever had the proper target on it," Hannah said. AOS is also working with the Missile Defense Agency to improve optics and avionics used on complicated missile defense interceptor seekers - or the "eyes" of a missile. "This is especially useful when (MDA) moves to using several kill vehicles on one interceptor," Farr said. "We are striving to make these lighter weight and less expensive. Multiple-kill vehicles on one interceptor mean multiple seeker heads. "If they weigh less and cost less then that's good all the way around."