Hubble Repairs Require 5th Spacewalk

Discovery’s astronauts ventured out for the fourth spacewalk in as many nights Sunday to patch insulation on the Hubble Space Telescope that’s peeling off like worn wallpaper.

Gregory Harbaugh and Joe Tanner took along swatches of material from emergency kits to cover the damaged thermal insulation and copper wire for fastening the pieces to the telescope.

There was not enough time to do all the repairs, so NASA ordered the crew to conduct an extra spacewalk tonight.

The repair was not considered urgent, but scientists did not want to wait until a servicing mission in late 1999. More sun damage to the insulation could allow Hubble’s electronics to overheat and could unbalance its mirrors.

“We’ve got a $2-billion investment here,” said Ed Weiler, NASA’s chief Hubble scientist. “Why take a chance?”

Sunday night’s spacewalk was supposed to be for equipping Hubble with new drive electronics for its solar panels and sturdier caps for its two magnetometers, part of the guidance system. Mission Control added some of the mending to the spacewalk.

The bulk of insulation repairs will be conducted during the spacewalk tonight by Mark Lee and Steven Smith, who installed three Hubble parts Saturday. The crew was supposed to spend tonight relaxing and gazing at Earth.

Discovery’s astronauts found the ruined insulation late last week. The worst damage was on the side of the telescope exposed to the sun.

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Only the outermost of 17 layers of Teflon insulation has peeled away and only in six places on the telescope, which is 43 feet long and 15 feet in diameter.

The extra work will push Hubble’s release from the shuttle from tonight to early Wednesday. Discovery is scheduled to land at Florida’s Kennedy Space Center early Friday.