Richard Lawrence - The Mammoth Book of Space Exploration and Disaster

In September 1993 US Vice-President Al Gore and Russian Prime Minister Viktor Chernomyrdin announced plans for Russia to help the US build a new International Space Station. As part of this agreement, NASA agreed to pay the Russian Space Agency $400 million to send five (later seven) astronauts to live aboard the Mir space station.

George Abbey was the NASA Director of Flight Operations involved in the development of the idea of merging the US and Russian Space Station programs. The program which was agreed was in three phases:

Phase One was a form of dress rehearsal consisting of seven four-and-a-half-month missions aboard the aging Russian space station Mir running from 1995 until mid 1998.

Phase Two would begin late in 1998 when the US and Russia would launch and lift the modules and components of a new International Space Station (ISS) requiring 43 separate missions, all assembled by EVA.

Phase Three would be the actual operation of the International Space Station (ISS).

Burrough:

On 17 July 1990 two cosmonauts, Anatoli Solovyov and Aleksandr Balandin were on the Mir space station. They needed to repair loose thermal blankets on their Soyuz capsule before they could return to earth. To do this they had to make an emergency EVA. Neither had been specially trained for space walking. Their preparation had consisted of watching some videotapes of training in the swimming pool at the Star City cosmonaut training centre. They used Mir’s Kvant 2 airlock to exit.

Before exiting the hatch, they had taken a pressure reading in the airlock. Either their handheld pressure gauge malfunctioned, or they misread it, because when they bent to open the hatch, there was still some air remaining in the airlock. The hatch immediately slammed outward on its hinges with terrific force.

The two cosmonauts then proceeded with the EVA, which proved dicier than anyone had expected. Fixing the thermal blankets took far longer than anticipated, and the spacewalk degenerated into a repair marathon that stretched past six hours. The space suits Solovyov and Balandin wore had only been rated for six and a half hours of use; when the two cosmonauts reached that point, the ground urgently ordered them to return to the airlock. Leaving their tools and ladders at the work site, Solovyov and Balandin were forced to scramble back across the length of Kvant 2 in total darkness, an exceedingly dangerous transit.

It was only when they reached the airlock and crawled inside that Solovyov realized the hinge had been damaged. The hatch wouldn’t close behind them. By this point the cosmonauts had been in a vacuum for nearly seven hours, and it was imperative that they find a way back inside the station. Clambering back outside the airlock, they tried the seldom-used backup airlock farther down Kvant 2, which to their relief opened and closed behind them. The EVA lasted seven hours and sixteen minutes.

The outer hatch, however, remained open to space. Solovyov and Balandin tried to fix it during a second spacewalk a week later, but it still wouldn’t close tightly. Then they discovered that a piece of the hinge cover had broken and lodged between the hatch and its frame. Removing the broken piece, they were finally able to close and repressurize the hatch. Several months later a new team of cosmonauts returned and found the hatch impossible to permanently repair. Instead they attached a set of clamps to secure it in place.

In 1962 the US National Academy of Sciences proposed building a large telescope that would allow astronomers to study the universe. The new telescope would be placed in orbit which would enable it to make observations free from atmospheric interference. The Hubble Space Telescope (HST) was named after Edwin Hubble, in 1929 who had observed that distant galaxies were moving away from us therefore the universe was expanding.

In 1977 the US Congress approved funding for the HST and construction of the telescope began.

In 1981 the Baltimore, Maryland-based Space Telescope Science Institute (STScI) became operational and the precision-ground mirror of the telescope was completed.

In 1985, construction of the entire HST was completed and the ground control facility for the telescope was established at the Space Telescope Operations Control Center in Goddard.

The Hubble Space Telescope should have resolving power ten times better than any ground-based telescope. It should be able to see objects which are fifty times fainter. In addition it would be able to observe wavelengths which are not detectable from the ground, particularly ultraviolet.

The launch of the HST was delayed due to the Challenger disaster in 1986, but in October 1989 the telescope was moved from Lockheed, California to its launch site at the Kennedy Space Center in Florida and on 24 April 1990 the HST was launched aboard the STS-31 mission of the Discovery space shuttle.

As soon as the Hubble Space Telescope was deployed in space, it became apparent that the primary mirror was the wrong shape. The 2.4 m concave mirror was too shallow by 2 mm at the edge and this caused light from the outer part of the mirror to converge to an F/24 focal point some 38 mm behind the light from the central region. As a result star images were surrounded by haloes, several being seconds in diameter instead of being pin sharp and only a fraction of a second in diameter. The primary mirror was clearly suffering from a severe case of spherical aberration, and it was later found that this was the result of faulty testing in the optical works, because one test component was 1.3 mm out of position. Five 6-hour space walks were required to repair the Hubble Space Telescope.

On 2 December 1993 the first servicing mission (STS-61) was launched aboard space shuttle Endeavour and on 4 December the mission commander, Colonel Richard Covey, piloted the shuttle to within 30 ft of the telescope. The astronauts, in pairs, did the necessary work during five spacewalks, a record for a single mission and four of the telescope’s six gyroscopes were replaced. On 5 December the two solar panels, which had been vibrating as a result of extreme changes in temperature, were replaced. On 6–7 December two astronauts replaced the Hubble’s primary camera, which had the flawed mirror, and also replaced two magnetic sensors, which measured the telescope’s position in the magnetic field. On 13 December the shuttle landed at Cape Canaveral, but it was another month before astronomers saw the first photographs from the repaired telescope. On 13 January 1994, NASA officials released photographs taken after the repairs, images that were much clearer than those taken earlier. One subject of the new photographs was the core of a galaxy 50 million light years distant. The astronauts had installed COSTAR (Corrective Optics Space Telescope Axial Replacement) to rectify the problem with the telescope’s primary mirror.

The instrument most affected by the poor images was the Wide Field and Planetary Camera, (WFPC), which the astronauts had completely replaced with a new one (WFPC2). WFPC2 incorporates secondary mirrors that have been deliberately figured high at the edges so that they introduce spherical aberration of the same magnitude as that of the HST primary mirror but of the opposite nature so that they should send corrected images to the CCD sensors.

The F/24 light beam from the main telescope is first fed to one of the instruments by a movable mirror. In the case of the WFPC the light then goes to a pyramid mirror which directs the beam into one of four CCD cameras. Each camera has a different focal length and one is chosen to give the most suitable size of image on the CCD sensor. The cameras are of the Cassegrain mirror type and it is the Cassegrain secondary mirror of each camera which has been specially figured with the right amount of spherical aberration.