ammonia Archives

December 24, 2013December 23, 2015 by Elizabeth Howell

Astronauts Brave Brief Ammonia Snowstorm As They Conclude Fix To Space Station

NASA astronaut Mike Hopkins holds a spare ammonia pump module during a spacewalk Dec. 24, 2013. Hopkins and fellow Expedition 38 Rick Mastracchio (top) performed two spacewalks to replace a pump blamed for crippling one of the International Space Station's two cooling loops Dec. 11. Credit: NASA TV (screenshot)

Toxic snowflakes in space were just one obstacle astronauts faced down today (Dec. 24) as they successfully replaced an ammonia pump that will, if all goes to plan, put the space station back in full service in a few hours.

“They’re just completely surrounding us now,” radioed NASA astronaut Rick Mastracchio of the ammonia flakes as the astronauts clipped four fluid lines into place on to the spare pump. NASA said the ammonia was just residual fluid and not indicative of a leak. “Some little ones, some big ones,” he added.

Within a few minutes, however, the ammonia dissipated. Some flakes did strike the spacesuits of Mastracchio and fellow NASA spacewalker Mike Hopkins, causing NASA to do a modified decontamination procedure where the astronauts stayed in a vacuum for a few extra minutes inside the airlock. (The sun’s heat bakes off ammonia over time, and the crew was outside long enough for most ammonia to dissipate, NASA said.)

The spacewalk completed with no further drama at 7 hours and 30 minutes, earning high praise for the participating astronauts from Mission Control in Houston.

“It’s the best Christmas ever,” radioed CapCom and NASA astronaut Doug Wheelock from the ground as the spacewalkers entered the International Space Station’s Quest airlock at the end of the repair job. “We got it,” Mastracchio responded.

NASA astronaut Doug Wheelock (left) and Japanese astronaut Aki Hoshide served as CapComs during two tricky ammonia pump replacements in December 2013. Wheelock assisted Expedition 38 spacewalking astronauts Mike Hopkins and Rick Mastracchio, while Hoshide helped Japanese astronaut Koichi Wakata with robotic maneuvers. Credit: NASA TV (screenshot)

Preliminary tests show the spare pump is working perfectly. The pump is a welcome present for the six-person Expedition 38 crew, which saw a reduction in science and backup systems for two weeks after a valve in the last pump failed, causing one of the station’s two cooling loops to shut down automatically. The loops are needed to regulate the temperatures of electronics and systems on station.

The Expedition 38 crew was so quick with the repair that they finished the job in two spacewalks instead of the planned three. The astronauts fell behind the timeline today as they struggled with some of the fluid connections to the new pump, but the final steps — putting the electrical connections in place — took just minutes. The pump was brought from another location on station today, and installed into its permanent spot to help ammonia flow through the cooling system.

Anywhere between hundreds and thousands of people at NASA and international partners scrambled to put spacewalks together to fix the cooling problem after it happened. Wheelock, himself a veteran of a tricky ammonia pump repair in 2010, communicated with the spacewalkers. Japanese astronaut Aki Hoshide filled the other CapCom slot, helping Japanese astronaut Koichi Wakata who handled robotics in orbit.

Japanese astronaut Koichi Wakata controlled Canadarm2 during two spacewalks to replace a faulty ammonia pump in December 2013. Credit: NASA TV (screenshot)

Mastracchio marked his eighth spacewalk with today’s repair while Hopkins, who rode Canadarm2 for the first time in a last-minute decision, was on his second. As with a spacewalk on Saturday (Dec. 21), the astronauts reported no helmet water leaks — comforting words for agency officials who put in new procedures and parts after an incident in July. (Mastracchio experienced a water problem during repressurization Saturday that was unrelated to the first incident, and wore a backup suit today to let the primary one dry out.)

Should the ammonia pump work as planned, this clears the way for the Russians to do a spacewalk Dec. 27 to install the Urthecast high-resolution camera that will beam live views of Earth, among other tasks. Expedition 38 has the day off tomorrow (Dec. 25), NASA TV added.

The only other Christmas Eve spacewalk in NASA history took place Dec. 24, 1999 during Hubble Space Telescope servicing mission STS-103. Another Christmas Eve milestone for NASA took place 45 years ago today, when the Apollo 8 crew made a now-famous broadcast while orbiting above the moon.

December 20, 2013December 23, 2015 by Elizabeth Howell

Watch Live As Astronauts Fix The Space Station Saturday

NASA astronaut Rick Mastracchio during a space station spacewalk on STS-131 in 2010. Credit: NASA

There’s a cooling problem on station, and two astronauts are ready to head outside to fix it. NASA astronauts Rick Mastracchio (a six-time spacewalker) and Mike Hopkins (a rookie) are expected to spend 6.5 hours “outside” starting at 7:10 a.m. EST (12:10 p.m. UTC) on Saturday. On robotics will be Japanese astronaut Koichi Wakata, who has operated every bit of robotics currently on station.

Click to watch Expedition 38’s crew action live above. (If for some reason the stream is not working, an alternate link is available here.) We’ll have full coverage of the spacewalk after it happens, too.

For a walkthrough of what’s going to happen, NASA handily provided a video that you can see below the jump. We also have links to all of our coverage so far.

In a nutshell, here’s what happened: a cooling loop shut down automatically on station Dec. 11 when the loop got too cold. NASA traced the problem to a faulty flow control valve inside of the pump. As agency officials prepared for a spacewalk just in case, NASA attempted to fix the valve and then control an alternate one from the ground.

However, the station is entering a time when there will be a lot of sun shining on it, making dockings and spacewalks difficult. To be prudent, NASA decided to do a spacewalk now and replace the pump. To keep the astronauts safe if another spacesuit leak happens again, the agency has introduced soaker pads and snorkels to the spacesuits.

Here’s what’s going to happen during the three spacewalks that are scheduled for Saturday, Monday (Dec. 23) and if necessary, Wednesday (Dec. 25), according to lead U.S. Spacewalk Officer Allison Bolinger:

December 20, 2013December 23, 2015 by Elizabeth Howell

After Facing Down Ammonia Leak, This Astronaut Will Help Crew During Spacewalks

NASA astronaut Doug Wheelock, who was commander of Expedition 25. This 2010 picture of him also shows the Sabatier system that extracts drinkable water from the International Space Station's atmosphere. Credit: NASA

When you learned to drive a car for the first time, remember how comforting it was to have an experienced driver beside you, able to anticipate the hazards and keep you on schedule?

That’s surely how the Expedition 38 crew feels about one of the voices “on the line” as two astronauts prepare to venture outside to replace a crippled ammonia pump. One of the “CapComs” or people communicating with the crew on Saturday, Monday and Wednesday will be astronaut Doug Wheelock — who just happens to be known for co-replacing a broken ammonia tank himself in 2010. (The other CapCom is Japanese astronaut Aki Hoshide, who will chat through robotic procedures with Koichi Wakata).

Wheelock is the visible edge of hundreds — likely thousands — of people working feverishly at NASA and its international partners this past week to get the spacewalks ready through pool simulations, a virtual reality lab and other means. Several backup and non-critical space station systems are offline because of that pump, which has to regulate temperatures properly for vital electronics to work.

“I am their choreographer,” Wheelock told Universe Today of his plan for the astronauts. While spacewalkers Mike Hopkins and Rick Mastracchio already know what they are supposed to do when, Wheelock said he will be “their eyes and ears on the timeline.” If something needs to be stopped or changed, he’ll help them figure out what to do next.

NASA astronaut Doug Wheelock anchored to Canadarm2 during an August 2010 spacewalk. He and Tracy Caldwell Dyson ventured outside three times during Expedition 24 to swap out and replace a broken ammonia pump. Credit: NASA

Wheelock and fellow astronaut Tracy Caldwell Dyson had to spring into action themselves in August 2010. A pump in the same location broke, forcing space station systems offline and requiring them to go outside a few days later. With astronaut Shannon Walker piloting Canadarm2, the astronauts accomplished their tasks in three spacewalks — but encountered obstacles along the way.

During the first spacewalk, as Wheelock disconnected lines from the broken pump, he not only faced a pipe that wouldn’t let go, but a shower of ammonia snowflakes. That was “what got me on the EVA [extra-vehicular activity],” he recalled. That’s why NASA plans to lower the line pressure on the cooling system before the astronauts head outside this time. Normally the lines are pressurized at 360 pounds per square inch, but they’ll be lowered to 120 psi through commands from the ground.

Other “lessons learned” are more recent. Italian astronaut Luca Parmitano was wearing a NASA spacesuit in July when he experienced a water leak in his helmet, putting him at risk and terminating the spacewalk early. This will be the first spacewalk since that time. NASA believes it has replaced the part of the suit that failed, but the agency has new backups in place. Hopkins and Mastracchio will have soaker pads in their helmets as well as a “snorkel”-like device, or tube that will let them breathe oxygen from a different part of the suit if water flows into the helmet again.

Allison Bolinger, NASA's lead U.S. spacewalk officer, holds up a snorkel-like device that astronauts began using in spacesuits in December 2013. The pipe (modified from spacesuit parts) is supposed to be a backup if a helmet fills with water, as what occurred during a July 2013 spacewalk. Credit: NASA (YouTube/screenshot) — Allison Bolinger, NASA’s lead U.S. spacewalk officer, holds up a snorkel-like device that astronauts began using in spacesuits in December 2013. The pipe (modified from spacesuit parts) is supposed to be a backup if a helmet fills with water, as what occurred during a July 2013 spacewalk. Credit: NASA (YouTube/screenshot)

So what are some key parts of the spacewalks to look for? Wheelock identified a few spots.

‘HAP’ check. That soaker pad is called a “helmet absorption pad”, and as a matter of course the astronauts will be asked to verify that the pad is not wet at the same time that they also check their gloves for tears (another lesson learned from a past spacewalk.) So you will hear Wheelock calling “HAP check” from time to time to the crew.

Unlatching and latching the ammonia connectors on the pumps. Because this is when leaks are most likely to occur — posing a risk to Mastracchio, who is performing the work — Wheelock is going to do a “challenge and response” procedure. He will read up the step, the astronaut will verify it and will do the work. There will be “a lot more chatter on the [voice] loop” during those times, Wheelock said, with everyone on the ground watching through Mastracchio’s head camera feed (visible at the front of the room) to see what is happening. “There will be a lot of people standing in Mission Control at that point,” he joked, himself included.

Leak procedures. If ammonia does start to shower out, Mastracchio will quickly close the valve and wait a few minutes as it could be just residual ammonia in the line. If that doesn’t work out, Mastracchio is trained on a procedure to attach a device to the front end of the connector and move a lever that prevents a cavity in the line from filling with ammonia. Then he can open the valve again, bleed out the ammonia that’s left over and keep going.

NASA astronaut Rick Mastracchio inspects two spacesuits to be used during spacewalks in December 2013. The spacewalks were to remove and replace a faulty ammonia pump. Credit: NASA TV

Decontamination procedures. The ammonia makes a distinctive “ping” when it hits the helmet, says Wheelock (who yes, heard that happen himself.) You can also see ammonia on the suit, he said, as it looks a bit like candle wax and obscures the stitching. All of which to say, NASA has procedures in place if the agency suspects or can confirm large amounts of ammonia got on Mastracchio’s suit. (Small amounts would essentially fleck off in the sun.) Hopkins, who will be out of the line of fire, can do a thorough inspection of Mastracchio and scrape off any ammonia with a warm metal tool — without hurting the suit underneath. The astronauts could also do a “bakeout” in the airlock — 30 minutes if suspected, an hour if confirmed — where they will sit with the hatch open and wait for any ammonia to sublimate off the suit. Once they close the hatch, the astronauts can verify if the ammonia is gone using Drager tubes, which have gold crystals inside that turn “purpleish blue” in the presence of ammonia, Wheelock said.

Margin calls. Because NASA needs to make sure the astronauts have 30 to 60 minutes to decontaminate at the end of their spacewalks, officials will preserve a margin of oxygen available for the astronauts to walk through that work. So it’s possible the agency may terminate a spacewalk before all tasks are completed just because they need that bit of margin at the end.

To learn more, Wheelock has been answering questions occasionally on his Twitter account from followers, and you can read through what he posts when he finds the time. Universe Today will also cover the spacewalks (currently planned for Saturday, Monday and Wednesday) as they occur.

December 16, 2013December 23, 2015 by Elizabeth Howell

Spacewalk, Or Backup Valve? NASA Works The Space Station Cooling Problem

The International Space Station as seen by the departing STS-134 crew aboard space shuttle Endeavour in May 2011. Credit: NASA

While Expedition 38 astronauts Rick Mastracchio and Michael Hopkins get their spacesuits and the Quest airlock ready in case they need to do a spacewalk to fix a cooling problem on board the station, NASA engineers have come up with an alternate proposal that could allow an interim fix from the ground.

A faulty flow control valve inside an external pump caused one of the station’s two main cooling loops to shut down automatically on Wednesday when the loop became too cold. This forced NASA to power down noncritical systems and some experiments as they moved the most needed systems on to a single loop.

After playing with the balky valve for several days, controllers determined it can’t be worked normally. Yet there is another valve nearby that possibly can.

Just “upstream” of the control valve is an isolation valve that possibly can be manipulated to control the temperature, said Kenny Todd, the ISS mission operations integration manager. While the valve is usually either open or closed to do its work, it is possible that it could be positioned at positions in between to warm up the coolant.

“Can we use it as a regulator, if you will, to restrict the flow coming from the radiator and by doing that, that would help to put the temperature in the loop a little warmer,” Todd said in an update broadcast on NASA Television today (Dec. 16) that you can watch in full below.

He added, “We’re taking a valve and using it for a different purpose than we’d originally intended.” This means that software must be adapted to control the valve from the ground, among other things. The hardware vendor (which Todd did not name) has said that theoretically this finer control would be possible.

It’s too early to say if this fix could work in the short term, let alone the long term, which is why Mastracchio and Hopkins are standing by ready to do a spacewalk if need be. NASA has experience with this kind of repair before, most notably in 2010 when astronauts aboard Expedition 24 performed three spacewalks to deal with a broken pump in the same cooling loop. There are three spare pumps aboard station that could swap out the crippled one.

NASA and Mastracchio have both said that the crew is doing fine. The largest scheduling changes are reportedly related to science experiments being suspended, as well as adding in some spacewalk preparation activities. Also, the Cygnus cargo spacecraft’s planned launch has been pushed back at least one day to Dec. 19; last week, NASA said the station’s cooling problem means it is violating certain “commit criteria” for the launch to move forward.

We’ll keep you updated as events warrant.

December 13, 2013December 23, 2015 by Elizabeth Howell

NASA Weighs Spacewalk To Fix Cooling Problem On Station

NASA may allow its first spacewalk since summer to deal with a malfunction that crippled a cooling loop on the International Space Station.

If extravehicular activity is deemed necessary for a fix, it would be the first time NASA spacesuits were used “outside” since Luca Parmitano, an Italian astronaut, experienced a water leak in one that cut short a spacewalk in July. NASA suspended all spacewalks as a precaution while the cause was investigated.

Since then, the agency has put in place procedures to protect astronauts from it happening again, opening up a spacewalk or spacewalks as an option to deal with a balky control valve inside a pump on the station.

The valve is an essential part of an S1 (starboard) truss pump that helps maintain the correct temperature for space station electronics. Ammonia circulates through two external cooling loops and is put through radiators to bleed off heat. The valve is required to mix the cool and warm parts of liquid in the ammonia loop.

Expedition 35 Flight Engineers Chris Cassidy (left) and Tom Marshburn completed a the 5-hour, 30-minute spacewalk on May 11 to inspect and replace a pump controller box on the International Space Station’s far port truss (P6) leaking ammonia coolant. Credit: NASA

A pump automatically shut down on Wednesday (Dec. 11) when the loop got too cold. As NASA began troubleshooting the issue, it powered down non-critical systems (including experiments and redundant systems) in the Columbus laboratory, Harmony node and Japanese Kibo laboratory. Primary systems are still online.

The astronauts are safe, NASA said today (Dec. 13), with the biggest impact to their activities being the science they perform. Expedition 38 astronaut Rick Mastracchio did a live media interview this morning (EST) where he similarly assured reporters that everyone on board is fine.

Cooling problems have happened on station before, most recently in May when an emergency spacewalk was needed to replace a pump controller box on the P6 (far port) truss. This particular cooling system experienced an issue in 2010, which required three contingency spacewalks to remove and replace a failed pump on the S1 truss.

Expedition 24 astronaut Douglas Wheelock exits the Quest airlock at the beginning of a spacewalk Aug. 11, 2010 to replace a failed ammonia pump on the International Space Station's S1 truss. Credit: NASA — Expedition 24 astronaut Douglas Wheelock exits the Quest airlock at the beginning of a spacewalk Aug. 11, 2010 to replace a failed ammonia pump on the International Space Station’s S1 truss. Credit: NASA

If a spacewalk is needed this time around, NASA has three spare pumps available on station for astronauts to use. NASA, however, is looking at all options before making a decision — including ways of controlling the errant valve from the ground. The agency is holding multiple meetings to decide what to do next after turning on and off the cooling loop yesterday and seeing the same malfunction.

On Monday, NASA will decide whether to move forward with a launch of a cargo spacecraft expected to head to the station on Dec. 18. The window for Orbital Sciences’ Cygnus spacecraft extends to Dec. 21 or 22, but as of Thursday (Dec. 12), the agency said the lack of redundant systems on station violates certain “commit criteria” for the launch to move forward.

While NASA spacewalks were suspended, activity using the Russian Orlan spacesuits has continued as usual. A spacewalk took place in November with the Olympic torch, amid other duties. Another spacewalk is planned Dec. 27 to install high- and medium-resolution cameras, put in a foot restraint, and remove and replace several external experiment packages.

December 12, 2013December 23, 2015 by Elizabeth Howell

UPDATE: NASA Pushes Back Cygnus Launch Decision Due To Space Station Cooling Problem

A view of the International Space Station as seen by the last departing space shuttle crew, STS-135. Credit: NASA

The decision to launch a cargo flight to the International Space Station next week has been pushed back until Monday (Dec. 16) because of a cooling problem on station that forced the shutdown of redundant systems, according to a NASA update.

Orbital Sciences’ Cygnus commercial spacecraft is expected to blast off on Dec. 18 from the Wallops Flight Facility in Virginia. However, with some station systems offline, the launch does not now meet certain “commit criteria” to make its journey to space next week, said Kenny Todd, the space station’s mission integration and operations manager.

“We haven’t lost any primary functionality,” he said in a NASA Television update today (Dec. 12), emphasizing that the six-person Expedition 38 crew is fine. “There is some redundancy that we’re down right now, but that’s not something I would call critical to day-to-day station operations.”

While a spacewalk is a possibility to fix the problem, it’s too early to say what NASA and other space station partners will decide to do.

NASA controllers spent the night examining a control valve blamed for causing an ammonia pump to shut down yesterday (Dec. 12). The space station uses liquid ammonia to maintain its temperature, pumping the ammonia through external radiators to bleed off heat. Astronauts have made periodic spacewalks to repair parts of the ammonia system, most recently in May when Expedition 35 replaced a pump controller box on the P6 (far port) truss just days before some crew members went home.

Expedition 35 Flight Engineers Chris Cassidy (left) and Tom Marshburn on a spacewalk on May 11 to inspect and replace a pump controller box on the International Space Station’s far port truss (P6) leaking ammonia coolant. Credit: NASA.

“The pump module on one of ISS two external cooling loops automatically shut down today when it got too cold,” stated the NASA Johnson Space Center Twitter feed yesterday (Dec. 11).

“The pump was brought back online, but they think a valve may not be working correctly inside it. Some of the station’s internal electrical systems were moved over to the second loop, and some noncritical things were powered down. The crew was always safe and will work with the ground teams as they figure out what caused the issue.”

Non-critical systems were powered down in the Harmony node, Columbus Laboratory and Japanese Kibo laboratory. After confirming that the new configuration was stable, controllers began this morning (EST) to move the troublesome valve to several positions and monitor the effect on cooling temperatures, according to a NASA TV update.

The Japanese Kibo module on the International Space Station as photographed by a member of the Expedition 38 crew in 2013. Credit: NASA

The crew is going about their activities as much as possible, although they’re on a “reduced timeline” because some of the experiments aren’t running as usual. (Science collected up to now is “not at risk”, Todd said.)

Responding to questions on social media, NASA astronaut Douglas Wheelock — who led three unplanned spacewalks in 2010 to replace a broken ammonia pump module on the S1 truss in the same cooling loop — said he is working with Mission Control to see what needs to be done next.

Of note, NASA has suspended spacewalks after a water leak in one of its spacesuits forced Italian astronaut Luca Parmitano back to the airlock during work in July. (Crewmate Chris Cassidy, who was on the spacewalk at the same time, later said he felt Parmitano was in no immediate danger, but felt the prudent thing to do was stop.)

NASA astronaut Douglas Wheelock during a contingency spacewalk Nov. 16, 2010 after an ammonia cooling pump failed aboard the International Space Station. During this spacewalk, Wheelock and fellow Expedition 24 crew member Tracy Caldwell installed a spare ammonia pump module on the S1 Truss on the space station. The duo did three contingency spacewalks during the mission to address the problem. Credit: NASA

Astronauts have been troubleshooting the suit periodically on board station, but NASA is planning to send it back on the next SpaceX Dragon flight to Earth for further investigation. SpaceX isn’t planning to get to the station again until late February, media reports say. Russian spacewalks can still continue as they use a separate suit; the most recent one took place in November with the Olympic torch.

While Todd didn’t quite say the ban on spacewalks has been lifted, he added that NASA has new procedures in place to guard against another crew member facing the same water issue. He did not elaborate on what those procedures are.

The current launch window for Cygnus extends as far as Dec. 21 and “possibly” the 22nd, Todd said, but emphasized more time is needed to come to a decision. “At this point, for lack of a better term, we’re going to kick the can a little bit and let the team work a little bit more,” he said.

Updates will follow as the situation and fix progresses.

September 7, 2012April 26, 2016 by Jason Major

Is Triton Hiding an Underground Ocean?

Voyager 2 mosaic of Neptune’s largest moon, Triton (NASA)

At 1,680 miles (2,700 km) across, the frigid and wrinkled Triton is Neptune’s largest moon and the seventh largest in the Solar System. It orbits the planet backwards – that is, in the opposite direction that Neptune rotates – and is the only large moon to do so, leading astronomers to believe that Triton is actually a captured Kuiper Belt Object that fell into orbit around Neptune at some point in our solar system’s nearly 4.7-billion-year history.

Briefly visited by Voyager 2 in late August 1989, Triton was found to have a curiously mottled and rather reflective surface nearly half-covered with a bumpy “cantaloupe terrain” and a crust made up of mostly water ice, wrapped around a dense core of metallic rock. But researchers from the University of Maryland are suggesting that between the ice and rock may lie a hidden ocean of water, kept liquid despite estimated temperatures of -97°C (-143°F), making Triton yet another moon that could have a subsurface sea.

How could such a chilly world maintain an ocean of liquid water for any length of time? For one thing, the presence of ammonia inside Triton would help to significantly lower the freezing point of water, making for a very cold — not to mention nasty-tasting — subsurface ocean that refrains from freezing solid.

In addition to this, Triton may have a source of internal heat — if not several. When Triton was first captured by Neptune’s gravity its orbit would have initially been highly elliptical, subjecting the new moon to intense tidal flexing that would have generated quite a bit of heat due to friction (not unlike what happens on Jupiter’s volcanic moon Io.) Although over time Triton’s orbit has become very nearly circular around Neptune due to the energy loss caused by such tidal forces, the heat could have been enough to melt a considerable amount of water ice trapped beneath Triton’s crust.

Another possible source of heat is the decay of radioactive isotopes, an ongoing process which can heat a planet internally for billions of years. Although not alone enough to defrost an entire ocean, combine this radiogenic heating with tidal heating and Triton could very well have enough warmth to harbor a thin, ammonia-rich ocean beneath an insulating “blanket” of frozen crust for a very long time — although eventually it too will cool and freeze solid like the rest of the moon. Whether this has already happened or still has yet to happen remains to be seen, as several unknowns are still part of the equation.

“I think it is extremely likely that a subsurface ammonia-rich ocean exists in Triton,” said Saswata Hier-Majumder at the University of Maryland’s Department of Geology, whose team’s paper was recently published in the August edition of the journal Icarus. “[Yet] there are a number of uncertainties in our knowledge of Triton’s interior and past which makes it difficult to predict with absolute certainty.”

Still, any promise of liquid water existing elsewhere in large amounts should make us take notice, as it’s within such environments that scientists believe lie our best chances of locating any extraterrestrial life. Even in the farthest reaches of the Solar System, from the planets to their moons, into the Kuiper Belt and even beyond, if there’s heat, liquid water and the right elements — all of which seem to be popping up in the most surprising of places — the stage can be set for life to take hold.

Read more about this here on Astrobiology.net.

Inset image: Voyager 2 portrait of Neptune and Triton taken on August 28, 1989. (NASA)