Astronauts aboard the International Space Station have conducted the second of three planned spacewalks to replace a failed module in the cooling system ammonia pump. The Extra Vehicular Activity (EVA) was carried out by astronauts Douglas Wheelock and Tracy Caldwell Dyson, the same pair who conducted the first. It was followed by NASA TV and NASA’s twitter feed.
The walk began at 13:27 BST, having been delayed by more than an hour to make further preparations. It began with that disconnect valve for the third and final line to the pump. This time, it disconnected easier and without a leak. The line was removed and examination appeared to show ice crystals were responsible for the previous problems. Five cables and four bolts later, the pump had a grapple bar placed onto it to enable it to be manhandled out of position. The thing was then positioned on the truss for storage and some preparations for the third spacewalk, which will install the spare pump, were done. Then the spacesuits were decontaminated and the walk ended after 7 hours and 26 minutes.
Highlights can be seen on NASA’s Youtube Channel and below:
The ISS isn’t the only thing having coolant issues at the moment. The infrared space survey telescope WISE is heating up. Infrared spacecraft are kept cool in order to prevent radiation from the warm probe overwhelming the signal from the cosmos. The Sun, which is required to shine on the spacecraft to generate electricity, heats the craft up and two coolant tanks keep the temperature low enough for the different sensors to pick out their signals. The operating temperature for WISE is 12 degrees Kelvin. The sensor operating at the longest wave radiation, detecting the coolest objects, was overwhelmed with radiation from the spacecraft as the secondary tank ran out of coolant and the probe warmed above 31 K. The primary tank still has plenty to go and should keep the spacecraft cool enough to conduct surveys with the remaining channels. The telescope completed an all sky survey with all channels operating and is presently rechecking half the sky to confirm previous observations and observe variations in signals.
The Alpha Magnetic Spectrometer, essentially a telescope for particles other than photons, is to be shown off to the press in Florida on the 26th of August before being prepared to head off to the ISS, where it will act as a new module. Further information and details on how accredited members of the media can apply to be there are here.
And finally, NASA’s efforts to spread the cost and energy of space activities has led to Isreal. The agency has signed a Statement of Intent for Future Cooperation with the Isreal Space Agency as part of ongoing efforts to foster international and interagency missions.