Hubble Engineers Push Robotic 'Evolution' To Save Telescope

Aviation Week & Space Technology 09/13/04
author: Frank Morring, Jr.

Robotic technology being developed out of necessity to keep the Hubble Space Telescope operating could also lead to new levels of man-machine teamwork in deep-space exploration down the road--if it survives the near-term scramble for funding.

Engineers here who have devoted their NASA careers to the concept of humans servicing the telescope in orbit are planning modifications to International Space Station (ISS) robots that would leave the humans on the ground. The work, forced by post-Columbia flight rules that killed a planned shuttle-servicing mission to Hubble, marks another step in the evolution of robot-partners for human space explorers.
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At a minimum a Hubble robotic mission must rendezvous with the telescope and attach a propulsion module for its eventual deorbiting. To extend its life by the five years that was the goal of a human mission, the telescope needs new batteries and gyros, and probably another replacement fine-guidance sensor to keep the observatory locked on distant objects for long exposures. To improve its performance, a new Wide Field Camera (WFC-3) and a Cosmic Origins Spectrograph (COS) had already been built at a cost of $83 million and $65 million, respectively, when the shuttle mission was canceled, but they were designed to be installed by astronauts. The mission concept taking shape at Goddard, guided by robotic tests with the Hubble high-fidelity mechanical simulator maintained here for astronaut training and configuration control, is still in what Burch describes as "somewhere between a formulation and a preliminary design stage." A two-part Hubble Robotic Vehicle (HRV) launched by a Delta IV or Atlas V would rendezvous with the telescope automatically and use a 39-ft. version of the Canadian robot arm on the ISS to grab one of two grapple fixtures on the barrel of the telescope, just as shuttle crews have done in the past.

The arm would then guide the HRV into position and drive it onto the so-called "towel bars," or berthing pins, on the telescope's aft shroud bulkhead that hold it in place in the shuttle cargo bay for servicing. The robot would be able to manage the highly precise three-dimensional alignment needed for berthing because its computer memory would contain the relevant portion of the computer-aided design (CAD) model that documents the configuration of the space telescope's aft shroud bulkhead.

Other CAD models would be uploaded to the robot throughout the 30-90-day mission as it performs its assigned tasks, giving it reference points to guide its robotic arms and tools with accuracy as close as 1/16 in., according to Cepollina. "The robot doesn't have enough capacity to store it all," he says.