All of the gerbils and half the mice reportedly did not survive their spaceflight aboard Russia’s Bion-M1 capsule, which returned to Earth last night after a month in space..

Anatoly Zak at RussianSpaceWeb.com cites Russia’s Interfax news agency as reporting that all eight Mongolian gerbils died because of an equipment failure.  Half of the 45 mice also did not survive, though no reason was given.  The 15 geckos (lizards) as well as the snails and containers of microorganisms and plants apparently are OK, however.

NASA is participating with Russia in this mission by providing animal enclosure units and performing research with the rodents (mice and gerbils).

A Russian spacecraft carrying a menagerie of animals that have been in orbit for a month is scheduled to land tonight, Saturday, May 18, Eastern Daylight Time (EDT).

The Bion-1M capsule was launched on April 19, the first of a new generation of Bion spacecraft.   NASA and Russia’s space agency collaborated on many of the earlier Bion flights, which ended in 1996 after U.S. animal rights groups protested the use of monkeys for such experiments.  One of the two monkeys on the 1996 flight died after it returned to Earth.

This flight carries no monkeys, but mice, gerbils, geckos, snails, and containers with various microorganisms and plants.   The flight has been dubbed an “orbital Noah’s Ark” or a “space zoo” because of the variety of animals aboard.  NASA is a partner in the fight, providing Animal Enclosure Units and participating in rodent research.

Landing is expected at 10:12 pm EDT (which will be May 19, 7:12 am Moscow Time, or May 19, 03:12 GMT) 82 kilometers north of Orenburg according to Anatoly Zak at RussianSpaceWeb.com  and Bob Christy at zarya.info.  Both have posted the ground track for the reentry.

Two International Space Station (ISS) crew members successfully replaced a coolant pump in the ISS electrical system today, but there was no sign of the leak that led to this unprecedented ISS spacewalk.

Tom Marshburn and Chris Cassidy completed their tasks about an hour ahead of schedule today, finishing the spacewalk in 5.5 hours.  One objective of the spacewalk, successfully executed, was replacing an ammonia pump used to cool a solar array channel that provides electricity for the ISS.  There are eight channels, one for each solar array.   ISS crew members noticed “snowflakes” emanating from one of them on Thursday, signalling an ammonia leak.  That channel had shown signs of leaks in the past, origin unknown, but this time the amount was much greater.

NASA decided to conduct an emergency spacewalk not because the leak posed a threat to the space station or the astronauts, but because they hoped to spot the source of the leak while ammonia was still being released.  That part of the assignment was unrealized.   When Marshburn and Cassidy arrived at the site, there was no sign of an ammonia leak.  They replaced the pump because it was one obvious source of the problem, and when the new pump was activated, no leak was observed.  That might be a cause for celebration, but NASA officials stressed at a post-spacewalk news conference that it will be many weeks before they feel they are certain the new pump resolves the issue.

“We are happy.  We are very happy,” said ISS Deputy Program Manager Joel Montalbano about the overall success of the spacewalk. This is the first time in the “increment” ISS missions that a spacewalk has been planned and executed in such a short period of time.  The desire to view the leak as it was occurring, and the experience of Marshburn and Cassidy — who conducted two spacewalks together on a 2009 space shuttle mission, including working in this area of the ISS — drove the decision to move quickly.  Marshburn will be returning to Earth on Monday after almost 5 months on the space station, so today was a unique opportunity.

NASA will hold a press briefing at 4:00 pm ET (3:00 pm CT) today about the ammonia leak on the International Space Station (ISS).

The briefing will be broadcast on NASA TV.  ISS Program Manager Mike Suffredini and NASA Chief Flight Director Norm Knight will discuss plans for assessing and fixing the leak, which ISS crew members noticed yesterday.  A final decision on whether to conduct a spacewalk on Saturday is expected later today.

In a spacewalk characterized as unprecedented for the International Space Station (ISS), two U.S. astronauts will venture outside their home in space Saturday morning to see if they can find and fix a vexing ammonia leak in the ISS electrical power system.

Tom Marshburn has been preparing for his return to Earth on Monday after nearly 5 months in space.   NASA officials stressed today that there is no change to the plan for Marshburn and two other ISS crewmembers to come home on Monday, but first he gets another chance to do a spacewalk.

Marshburn and Chris Cassidy, who is part of a different set of ISS crewmembers that is remaining onboard the station, have already done two spacewalks together (on STS-127 in 2009) and worked in the area where they need to go tomorrow.  Their experience helped NASA officials decide that it was OK to go ahead with this spacewalk with less than 48 hours notice.  NASA chief flight director Norm Knight said that performing a spacewalk with so little advance planning is “precedent setting” for ISS missions (called “increments”), though perhaps not for space shuttle flights. 

ISS crewmembers observed “snowflakes” coming off one of the ISS solar array trusses yesterday that was quickly determined to be an ammonia leak in one of the eight power channels that provide electricity.  There is one power channel for each solar array.  Ammonia is used as a coolant.

This leak is in the vicinity of a previous leak that NASA was never able to identify so it is not known if something happened to increase that leak or if this is something unrelated.   ISS program manager Mike Suffredini stressed the difficulty of finding leaks, which may come from very tiny holes, perhaps caused by a Micrometeoroid Orbital Debris (MMOD) hit.  Or the leak may be from a seal in the pump.  They simply don’t know.  Marshburn and Cassidy will do a visual inspection and replace the pump.

The decision to do a spacewalk quickly was driven largely by the desire to observe the leak when a lot of ammonia is being released precisely so that the source can be identified.   The ammonia in the system is expected to be depleted in a day or so. 

The opportunity to discover the source of the leak coupled with the experience of these two ISS crew members were major factors in the decision to go ahead with the spacewalk tomorrow, Suffredini said.   It is not a matter of an emergency situation aboard the station.  The crew is in no danger from the leak and the ISS can operate with minimal impact using the other seven channels.   If the astronauts cannot identify the source of the leak and replacing the pump does not remedy the situation, the ISS can continue operating almost normally at least in the short term.   For the long term, operating with only seven instead of eight electrical channels could reduce the amount of research that can be conducted.   This is “not critical from a safety standpoint,” Suffredini said, but “if we have to live with this channel down for a long period of time” it will have an impact on research.   The main purpose of the ISS is to serve as a scientific research laboratory for experiments that need to be conducted in microgravity.

Marshburn and Cassidy are scheduled to open the hatch to exit the ISS at 8:15 am Eastern Daylight Time  (EDT) tomorrow morning (7:15 am Central Daylight Time).   During the 6 hour 15 minute spacewalk, they will inspect the area of the leak and replace the pump.   They then will inspect each other’s spacesuits for signs of ammonia contamination since NASA knows there is a lot of leaked ammonia in the area.   A 30-45 minute “bake out” period will ensue as a precaution to allow any unnoticed ammonia to evaporate.  They will then reenter the airlock and pressurize it to 5 pounds per square inch (psi) where another test will be conducted to ensure they are not bringing any ammonia into the station before full repressurization.

Marshburn, Russian cosmonaut Roman Romanenko and Canadian astronaut Chris Hadfield remain on schedule to return to Earth on Monday, May 13, in their Soyuz TMA-07M spacecraft.  Undocking is scheduled for 7:08 pm EDT, with landing at 10:31 pm EDT (8:31 am May 14 local time at the landing site in Kazakhstan).  They were launched on December 19, 2012.

NASA TV will cover tomorrow’s spacewalk beginning at 7:00 am EDT (6:00 am CDT).   It also will cover the landing on Monday, as detailed in NASA’s press release.

NASA reports that astronauts aboard the International Space Station (ISS) noticed a significant exterior ammonia leak beginning about 11:30 am Eastern Daylight Time (EDT) today.  The agency stresses that the astronauts are in no danger.

The crew noticed small white flakes floating away from a portion of one of the solar arrays where part of the cooling system is located.  Ammonia is used as a coolant for the power channels that provide electricity generated by the solar arrays.  Crew observations and images obtained from exterior cameras operated by ground controllers confirmed that it is in the same area where a leak was investigated during a November 2012 spacewalk. 

NASA said it is making plans to reroute other power channels to ensure full operation of the space station.   The leak rate is so high that a complete shutdown of that cooling loop might be required in the next 48 hours.