orbital adjustments were made 4 and 5 June, and Progress 6 was undocked 8 June. Soyuz 34, launched uncrewed on 6 June, docked at the just-vacated aft port of the space station on 9 June. The Soyuz had a new engine system, and its successful test flight gave the Salyut 6 crew a reliable return vehicle. Since the craft was uncrewed, some biological samples for experiments were included on the flight. Soyuz 32 was loaded with 130 kg of replaced instruments, processed materials, exposed film and other items with a total weight equal to that of the two cosmonauts. On 13 June, it undocked and returned to Earth uncrewed 295 km northwest of Dzhezkazgan. The next day, the crew redocked Soyuz 34 at the forward port to clear the aft port for Progress 7. Progress 7, radio telescope deployed, return to Earth Progress 7 was launched 28 June and docked at Salyut 6 two days later. It carried 1,230 kg of supplies including food, plants, mail and a 10-metre diameter radio telescope. The station's orbit was raised 3 and 4 July to a 399–411 km orbit, the highest at which a Salyut had operated. This was because no more Progress flights were planned for 1979 and the Salyut's propulsion system was suspect, so the decision was to raise the station's orbit as high as possible before the crew returned to Earth. Propellant was transferred by 17 July. When the Progress craft undocked, the wire mesh parabolic telescope was unfurled. A camera aboard the tanker beamed the scene to Earth. The KRT-10 radio telescope was deployed out of the rear docking port, but results proved disappointing and the cosmonauts ejected it on August 9. Trouble happened again when the antenna became snared on the port, forcing the tired cosmonauts to perform an unscheduled space walk on 15 August to cut it loose. Ryumin, attached to a tether, used hand rails to get to the antenna and cut it away. Then he and Lyakhov retrieved a materials experiment left on the station's exterior. Because the space walk was so late in the mission, the crew was apprehensive as they were not in the best physical condition to carry it out, so they left letters in the Soyuz return vehicle in case they did not survive. They packed several experiments in Soyuz 34 and departed the space station 19 August, reentering two days