How Do Cats Deal With Being Weightless?

Since my previous post was about dogs, its time to give equal time to the cats … although I’m guessing the cat lovers of the world won’t have a great reaction to this one. Here’s some footage from some the Aerospace Medical Research Laboratories which include a test of the effects of weightlessness on cats in a C-131 “vomit comet” that simulates weightlessness. Best I can tell, this research was done in 1947. Think of it in the same vein as all those weird tests the early astronauts had to endure.

The text from the video: “In these experiments you can see the disorientation resulting when an animal is suddenly placed in a weightless state. Cats when dropped under normal conditions will invariably rotate their bodies longitudinally in midar and land on their feet. This automatic reflex action is almost completely lost under weightlessness.”

The research was conducted by Bioastronautics Research, part of the Air Force and the Department of Defense.

Amy Shira Teitel has a great post about the early medical tests on astronauts: As she wrote, “The Mercury astronauts only half joked during a 1959 press conference that the doctors had probed every orifice the human male has to offer, and then some, all in the name of ‘science’.”

NASA Launches Revolutionary Earth Science Satellite Measuring Soil Moisture Cycle

NASA’s Soil Moisture Active Passive (SMAP) observatory, on a United Launch Alliance Delta II rocket, is seen after the mobile service tower was rolled back Friday, Jan. 30 at Space Launch Complex 2, Vandenberg Air Force Base, Calif.
Image Credit: NASA/Bill Ingalls
Story updated[/caption]

At dawn this morning (Jan. 31) NASA launched an advanced Earth science satellite aimed at making measurements of our planet’s surface soil moisture and freeze/thaw states from space that will revolutionize our understanding of the water, energy, and carbon cycles driving all life on Earth, aid weather forecasting and improve climate change models.

NASA’s new Soil Moisture Active Passive (SMAP) observatory thundered off the pad at 6:22 a.m. PST (9:22 a.m. EST) Saturday atop a two stage United Launch Alliance Delta II rocket from Space Launch Complex 2 on Vandenberg Air Force Base, California.

The $916 million satellite successfully separated from the rocket’s second stage some 57 minutes after the flawless liftoff and was injected into an initial 411- by 425-mile (661- by 685-kilometer) orbit. The spacecraft then deployed its solar arrays and telemetry indicated it was in excellent health.

“We’re in contact with SMAP and everything looks good right now,” NASA Launch Manager Tim Dunn said.

“Deployment of the solar arrays is underway. We just couldn’t be happier.”

SMAP separated from the second stage while pointed toward the sun as seen in the video below from a rocket mounted camera:

Video Caption: A camera on the second stage of the Delta II rocket captured this footage as the SMAP spacecraft pushed itself away from the rocket to complete the delivery of the Earth-observing spacecraft to its proper orbit following Jan. 31, 2015 liftoff. Credit: NASA TV/ULA

SMAP is NASA’s 1st Earth observing satellite designed to make high resolution global observations of Earth’s vital surface soil moisture content and freeze/thaw cycle just below your feet. It will aid global forecasting and have broad applications for science and society.

SMAP’s combined radar and radiometer instruments will peer into the top 2 inches (5 centimeters) of soil, through clouds and moderate vegetation cover, day and night, to produce the highest-resolution, most accurate soil moisture maps ever obtained from space, says NASA.

The blastoff of SMAP successfully concluded NASA’s ambitious plans to launch a record breaking total of five Earth science satellites in less than a year’s time.

“The launch of SMAP completes an ambitious 11-month period for NASA that has seen the launch of five new Earth-observing space missions to help us better understand our changing planet,” said NASA Administrator Charles Bolden.

“Scientists and policymakers will use SMAP data to track water movement around our planet and make more informed decisions in critical areas like agriculture and water resources.”

Artist's rendering of the Soil Moisture Active Passive satellite. The width of the region scanned on Earth’s surface during each orbit is about 620 miles (1,000 kilometers).  Image credit: NASA/JPL-Caltech
Artist’s rendering of the Soil Moisture Active Passive satellite. The width of the region scanned on Earth’s surface during each orbit is about 620 miles (1,000 kilometers). Image credit: NASA/JPL-Caltech

SMAP is projected to last for at least a three year primary mission.

The prior NASA Earth science instrument launched was the Cloud Aerosol Transport System (CATS) payload hauled to space by the SpaceX CRS-4 Dragon on Jan. 10, 2015 and recently installed on the exterior of the ISS. Read my CATS installation story – here.

The three earlier NASA Earth science missions launched over the past year included ISS-RapidScat in September 2014, the Global Precipitation Measurement (GPM) Core Observatory, a joint mission with the Japan Aerospace Exploration Agency, in February 2014, and the Orbiting Carbon Observatory-2 (OCO-2) carbon observatory in July 2014.

“Congratulations to the NASA Launch Services Program team, JPL and all of our mission partners on today’s successful launch of the SMAP satellite,” said Jim Sponnick, ULA vice president, Atlas and Delta Programs.

“It is our honor to launch this important Earth science mission to help scientists observe and predict natural hazards, and improve our understanding of Earth’s water, energy and carbon cycles.”

SMAP will provide high-resolution, space-based measurements of soil moisture and its state — frozen or thawed — a new capability that will allow scientists to better predict natural hazards of extreme weather, climate change, floods and droughts, and help reduce uncertainties in our understanding of Earth’s water, energy and carbon cycles, according to a NASA description.

The mission will map the entire globe every two to three days for at least three years and provide the most accurate and highest-resolution maps of soil moisture ever obtained. The spacecraft’s final circular polar orbit will be 426 miles (685 kilometers), at an inclination of 98.1 degrees. The spacecraft will orbit Earth once every 98.5 minutes and repeat the same ground track every eight days.

“All subsystems are being powered on and checked out as planned,” Kent Kellogg, the SMAP project manager, during a post-launch press conference.

“Communications, guidance and control, computers and power are all operating nominally.”

The observatory is in excellent health. Its instruments will be turned on in 11 days.

Today’s blastoff of SMAP marks ULA’s second successful launch this month as well as the second of 13 planned for 2015. ULA’s first launch of 2015 was MUOS-3 from Cape Canaveral on Jan. 20.

ULA’s next launch involves NASA’s Magnetospheric Multiscale Mission (MMS) to study Earth’s magnetic reconnection. It is scheduled for launch on an Atlas V 421 booster on March 12 from Cape Canaveral. See my up close visit with MMS and NASA Administrator Charles Bolden at NASA Goddard Space Flight Center detailed in my story – here.

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

SpaceX Dragon Captured at Station Loaded with Critical Supplies and Science

The commercial SpaceX cargo Dragon, loaded with over 2.6 tons of critically needed supplies and science experiments, was captured by the crew aboard the International Space Station (ISS) this morning (Jan. 12) while soaring over the Mediterranean Sea.

The SpaceX Dragon CRS-5 cargo vessel arrived at the station following a flawless two day orbital pursuit and spectacular nighttime blastoff atop the SpaceX Falcon 9 on Jan. 10 at 4:47 a.m. EST from Cape Canaveral Air Force Station in Florida.

Note: This breaking news story is being updated. Check back frequently for updates.

Dragon was successfully berthed and bolted into place a few hours later at 8:54 a.m. EST.

Working at the robotics work station inside the seven windowed domed cupola, Expedition 42 Commander Barry “Butch” Wilmore of NASA, with the assistance of Flight Engineer Samantha Cristoforetti of the European Space Agency, successfully captured the Dragon spacecraft with the station’s Canadian-built robotic arm at 5:54 a.m. EST.

Wilmore grappled Dragon with the station’s 57-foot-long (17-meter-long) robotic arm at 5:54 a.m. EST, about 18 minutes ahead of schedule, in an operation shown live on NASA TV, back-dropped by breathtaking views of “our beautiful Earth” passing by some 260 miles (410 kilometers) below.

Among the goodies aboard are belated Christmas presents for the crew. The Falcon 9 and Dragon were originally scheduled to liftoff in December and arrive in time for the Christmas festivities.

The cargo freighter flew beneath the station to arrive at the capture point 32 feet (10 meters) away. Dragon’s thrusters were disabled at the time of grappling.

Robotics officers at Houston Mission Control then began remotely maneuvering the arm to berth Dragon at the Earth-facing port on the station’s Harmony module starting at 7:45 a.m. EST.

Dragon is being attached via the common berthing mechanism (CBM) using four gangs of four bolts apiece to accomplish a hard mate to Harmony. The overall grappling and berthing process requires a few hours.

Dragon was successfully berthed and bolted into place at 8:54 a.m. EST and its now part of the space station.

The crew will conduct leak pressure checks, remove the docking mechanism and open the hatch later today or tomorrow.

#Dragon is about 90 feet from #ISS, closing in on its capture point.  Credit: NASA TV
#Dragon is about 90 feet from #ISS, closing in on its capture point. Credit: NASA TV

CRS-5 marks the company’s fifth operational resupply mission to the ISS under a $1.6 Billion contract with NASA to deliver 20,000 kg (44,000 pounds) of cargo to the station during a dozen Dragon cargo spacecraft flights through 2016 under NASA’s Commercial Resupply Services (CRS) contract.

Overall this is the sixth Dragon to arrive at the ISS.

The ISS cannot function without regular deliveries of fresh cargo by station partners from Earth.

The Dragon CRS-5 spacecraft is loaded with over 5108 pounds (2317 kg) of scientific experiments, technology demonstrations, crew supplies, spare parts, food, water, clothing, and assorted research gear for the six person crew serving aboard the ISS.

Among the payloads is the Cloud-Aerosol Transport System (CATS), a remote-sensing laser instrument to measure clouds and the location and distribution of pollution, dust, smoke, and other particulates and aerosols in the atmosphere that directly impact the global climate.

CATS is loaded aboard the unpressurized trunk of Dragon.

Also loaded onboard are 17 student experiments known collectively as the “Yankee Clipper” mission. The experiments are sponsored by the National Center for Earth and Space Science Education, which oversees the Student Spaceflight Experiments Program (SSEP) in partnership with NanoRacks LLC.

The launch marked the first US commercial resupply launch since the catastrophic destruction of an Orbital Sciences Antares rocket and Cygnus Orb-3 spacecraft bound for the ISS which exploded unexpectedly after launch from NASA Wallops, VA, on Oct. 28, 2014.

The US supply train to the ISS is now wholly dependent on SpaceX until Cygnus flights are resumed, hopefully by late 2015, on an alternate rocket, the Atlas V.

SpaceX Falcon 9 rocket lifts off from Space Launch Complex 40 at Cape Canaveral Air Force Station, Fl, carrying the Dragon resupply spacecraft to the International Space Station.   Credit: John Studwell/AmericaSpace
SpaceX Falcon 9 rocket lifts off from Space Launch Complex 40 at Cape Canaveral Air Force Station, FL, carrying the Dragon resupply spacecraft to the International Space Station. Credit: John Studwell/AmericaSpace

Dragon will remain attached to the ISS for about four weeks until Feb. 10.

SpaceX also had a secondary objective of recovering the Falcon 9 booster’s first stage via an unprecedented precision guided landing on an ocean-going “drone.”

The history making attempt at recovering the Falcon 9 first stage was a first of its kind experiment to accomplish a pinpoint soft landing of a rocket onto a tiny platform in the middle of a vast ocean using a rocket assisted descent.

In my opinion the experiment was “a very good first step towards the bold company goal of recovery and re-usability in the future” as I wrote in my post launch report here at Universe Today.

Listen to my live radio interview with BBC 5LIVE conducted Saturday night, discussing SpaceX’s first attempt to land and return their Falcon-9 booster.

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

The SpaceX Dragon is attached to the Harmony module. Credit: NASA TV
The SpaceX Dragon is attached to the Harmony module. Credit: NASA TV

SpaceX and NASA On Track For Spectacular Predawn Jan. 6 Launch of Critical Cargo Mission to ISS

SpaceX is on track to rollout their Falcon 9 rocket carrying the Dragon cargo freighter this evening, Monday, Jan, 5, 2015 to launch pad 40 on a mission bound for the International Space Station (ISS) to deliver critical supplies.

The Dragon CRS-5 mission is slated to blast off at 6:20 a.m. EST, Tuesday, Jan. 6, 2015, atop the SpaceX Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida.

The predawn launch should put on a spectacular sky show for spectators along the Florida space coast.

There is only an instantaneous launch window available, meaning that the blastoff must proceed at that exact instant. Any delays due to technical issues or weather would force a scrub until at least Friday, Jan. 9.

SpaceX Falcon 9 ready for rollout to launch pad for Dragon CRS-5 mission.  Credit: SpaceX
SpaceX Falcon 9 ready for rollout to launch pad for Dragon CRS-5 mission. Credit: SpaceX

The launch has already been postponed several times, most recently from Dec. 19, 2014 when a static fire test of the first stage engines on Dec. 17 shut down prematurely.

A second static fire test of the SpaceX Falcon 9 successfully went the full duration of approximately 3 seconds and cleared the path for a liftoff attempt after the Christmas holidays.

The delay allowed the teams to recoup and recover and enjoy the festive holiday season.

“It was a good decision to postpone the launch until after the holidays,” said Hans Koenigsmann, VP of Mission Assurance, SpaceX, at a media briefing today at the Kennedy Space Center (KSC).

Following the catastrophic failure of the Orbital Sciences Antares rocket and Cygnus cargo freighter on Oct. 28 from NASA’s Wallops Flight Facility in Virginia, officials have been prudently cautious to ensure that all measures were carefully rechecked to maximize the possibilities of a launch success.

SpaceX Falcon 9 rocket completes successful static fire test on Dec. 19 ahead od planned CRS-5 mission for NASA in early January 2015. Credit:  SpaceX
SpaceX Falcon 9 rocket completes successful static fire test on Dec. 19 ahead od planned CRS-5 mission for NASA in early January 2015. Credit: SpaceX

CRS-5 marks the company’s fifth resupply mission to the ISS under a $1.6 Billion contract with NASA to deliver 20,000 kg (44,000 pounds) of cargo to the station during a dozen Dragon cargo spacecraft flights through 2016 under NASA’s Commercial Resupply Services (CRS) contract

The weather odds have improved to 70% GO from 60% GO reported Major Perry Sweat, 45th Weather Squadron rep, USAF, at the briefing today at the Kennedy Space Center.

A frontal boundary has settled in over Central Florida. This front and its associated cloudiness will be very slow to move south of the Space Coast. With the clouds only slowly eroding overhead, the primary weather concern remains thick clouds, according to Sweat.

The unmanned cargo freighter is loaded with more than 5108 pounds (2317 kg) of scientific experiments, technology demonstrations, crew supplies, spare parts, food, water, clothing and assorted research gear for the space station.

The Dragon research experiments will support over 256 science and research investigations for the six person space station crews on Expeditions 42 and 43.

Among the payloads is the Cloud-Aerosol Transport System (CATS), a remote-sensing laser instrument to measure clouds and the location and distribution of pollution, dust, smoke, and other particulates and aerosols in the atmosphere.

Commander Barry “Butch” Wilmore on the International Space Station shared this beautiful image of #sunrise earlier today, 1/3/15.  Credit: NASA/Barry ‘Butch’ Wilmore
Commander Barry “Butch” Wilmore on the International Space Station shared this beautiful image of #sunrise earlier today, 1/3/15. Credit: NASA/Barry ‘Butch’ Wilmore

Assuming all goes well, Dragon will rendezvous at the ISS on Thursday, Jan. 8, for grappling and berthing by the ISS astronauts maneuvering the 57 foot-long (17 meter-long) Canadian built robotic arm.

The SpaceX CRS-5 launch is the first cargo launch to the ISS since the doomed Orbital Sciences Antares/Cygnus launch ended in catastrophe on Oct. 28.

With Antares launches on indefinite hold, the US supply train to the ISS is now wholly dependent on SpaceX.

Orbital Sciences has now contracted United Launch Alliance
(ULA) to launch the firms Cygnus cargo freighter to the ISS by late 2015 on an Atlas V rocket.

A secondary objective of SpaceX is to attempt to recover the Falcon 9 first stage on an off shore barge.

NASA Television live launch coverage begins at 5 a.m. EST on Jan. 6.

 SpaceX Falcon 9 rocket is set to soar to ISS after completing  successful static fire test on Dec. 19 ahead of planned CRS-5 mission for NASA in early January 2015. Credit: Ken Kremer – kenkremer.com
SpaceX Falcon 9 rocket is set to soar to ISS after completing successful static fire test on Dec. 19 ahead of replanned CRS-5 mission for NASA launching on Jan. 6, 2015. Credit: Ken Kremer – kenkremer.com

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

New countdown clock at NASA’s Kennedy Space Center displays SpaceX Falcon 9 CRS-5 mission and recent Orion ocean recovery at the Press Site viewing area on Dec. 18, 2014.  Credit: Ken Kremer – kenkremer.com
New countdown clock at NASA’s Kennedy Space Center displays SpaceX Falcon 9 CRS-5 mission and recent Orion ocean recovery at the Press Site viewing area on Dec. 18, 2014. Credit: Ken Kremer – kenkremer.com

Space Station to Get a ‘Laser Cannon’

What’s a space station without a laser cannon?

The International Space Station will be getting its very own laser at the end of 2014. And unlike the planet-smashing capabilities of the Death Star of Star Wars fame, this laser will to be enlisted for the purpose of science.

It’s called CATS, and no, it isn’t the latest attempt to put feline astronauts in space. CATS stands for the Cloud Aerosol Transport System. The goal of CATS is to study the distribution of tiny particles of dust and air contaminants known as aerosols.

Developed by research scientist Matt McGill at NASA’s Goddard Space Flight Center in Greenbelt Maryland, CATS is slated to head to the International Space Station later this year on September 12th aboard SpaceX’s CRS-5 flight of the Dragon spacecraft. CATS will be installed on the Japanese Experiment Module-Exposed Facility (JEM-EF) and will demonstrate the utility of state-of-the-art multi-wavelength laser technology to study aerosol distribution and transport in the atmosphere.

Such knowledge is critical in understanding the path and circulation of aerosols and pollutants worldwide. When the Eyjafjallajökull volcano erupted in Iceland back in 2010, many trans-Atlantic flights were grounded as a precaution. These measures are necessary as several flights have suffered engine failures in the past due to encounters with volcanic ash clouds, such as the four engine failure of KLM Fight 867 in 1989 and the British Airways Flight 9 incident over Southeast Asia in 1982. Knowing where these dangerous ash clouds are is crucial to the safety of air travel.

The expanding ash cloud spewing from Iceland's Eyjafjallajökull volcano as seen from space in 2010. Credit: NASA.
The expanding ash cloud spewing from Iceland’s Eyjafjallajökull volcano as seen from space in 2010. Credit: NASA.

To accomplish this, CATS will emit 5,000 1 milliJoule laser pulses a second at the 1064, 532 and 355 nanometer wavelengths.  This represents a vast improvement in power requirements and thermal capabilities over a similar instrument currently in service aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Earth remote sensing spacecraft.

And it’s that third 355 nanometer wavelength that will make CATS stand out from CALIPSO. This will also allow researchers to differentiate between particle size and measure the horizontal and vertical distribution of aerosol particles in the atmosphere. CATS will also be capable of measuring the number of individual photons being reflected back at it, which will provide a much better resolution and understanding of current atmospheric activity.

“You get better data quality because you make fewer assumptions, and you get, presumably, a more accurate determination of what kind of particles you’re seeing in the atmosphere,” McGill said in a recent press release.

The International Space Station also provides a unique vantage point for CATS. In a highly inclined 51.7 degree orbit, the station passes over a good swath of the planet on 16 orbits daily on a westward moving ground track that repeats roughly every three days. This will assure CATS has coverage over a large percentage of the planet, including known pollutant transport routes across the northern Pacific and down from Canada over the U.S. Great Lakes region.

While the first two lasers will operate in the infrared and visual wavelengths, said third laser will work in the ultraviolet. And while this will give CATS an enhanced capability, engineers also worry that it may also be susceptible to contamination.  “If you get contamination on any of your outgoing optics, they can self-destruct, and then your system is dead. You end up with a very limited instrument lifetime,” McGill said.

Still, if CATS is successful, it may pave the way for larger, free-flying versions that will monitor long-range atmospheric patterns and shifts in climate due to natural and man-made activity. And the ISS makes a good platform to test pathfinder missions like CATS at low cost. “In our current budget-constrained environment, we need to use what we already have, such as the [station], to do more with less,” McGill said.

CALIPSO's LiDAR imaged from the ground by Gregg Hendry in 2008. Used with permission.
CALIPSO’s LiDAR imaged from the ground by Gregg Hendry in 2008. Used with permission.

The advent of a LiDAR system aboard the ISS has also generated a spirited discussion in the satellite tracking community concerning prospects for spotting CATS in operation from the ground. The CALIPSO LiDAR has been captured by ground spotters in the past. However, CALIPSO fires a much more powerful 110 milliJoule pulse at a rate of 20 times a second. Still, the lower power CATS system will be firing at a much faster rate, delivering a cumulative 5,000 milliJoules a second.  CATS won’t be bright enough to show up on an illuminated pass of the ISS, but it just might be visible during darkened passes of the ISS through the Earth’s shadow. And, unlike CALLIPSO — which is part of the difficult to observe A-Train of Earth-observing satellites — the ISS passes in view of a majority of humanity. At very least, activity from CATS will be worth watching out for, and may well be seen either visually or photographically.

We’ll soon be adding CATS to the long list of outstanding science experiments being conducted aboard the International Space Station, and the sight of this “fully armed and operational battle station” may soon be coming to a dark sky site near you!

Dusty, Windy And Damp: Five NASA Probes To Hunt Down Climate Change in 2014

How badly will climate change affect our planet? Different models tell us different things, and that’s partly because we need more precise information about the factors that warm the world. How much is sea level rising? What are the levels of carbon dioxide in the atmosphere? All of these things must be known.

NASA expects to launch five Earth science missions this year, which is the biggest roster in more than a decade. They’ll track rainfall, seek water hiding in soil, and examine carbon dioxide and ocean winds around the world. Here’s a quick rundown of the busy launch schedule:

Global Precipitation Measurement (GPM) Core Observatory (Feb. 27): This will be the first of a series of satellites to look at snow and rain from space. “This new information will help answer questions about our planet’s life-sustaining water cycle, and improve water resource management and weather forecasting,” NASA stated. This joint spacecraft with the Japanese Aerospace Exploration Agency (JAXA) will launch from Japan’s Tanegashima Space Center on a H-IIA rocket. GPM was built at NASA’s Goddard Space Flight Center in Maryland.

ISS-RapidScat (June 6): This sensor will sit on the International Space Station and monitor ocean winds (including storms and hurricanes). What’s interesting about this mission is its use of old parts, NASA points out, as well as the decision to mount it on a station rather than take the more expensive route of making it a separate satellite. The probe will launch on a SpaceX Dragon spacecraft (aboard a SpaceX Falcon 9 rocket) from Florida’s Cape Canaveral Air Force Station as part of a regular commercial resupply flight.

Artist's conception of how ISS-RapidScat will work. Credit: NASA/JPL-Caltech/Johnson Space Center
Artist’s conception of how ISS-RapidScat will work. Credit: NASA/JPL-Caltech/Johnson Space Center

Orbiting Carbon Observatory (OCO)-2 (July): NASA plans to take a second crack at this type of satellite after the OCO launch failure in 2009. The satellite will seek out carbon dioxide to better understand where it is emitted (in both natural and artificial processes) and how it moves through the water, air and land. This will launch from California’s Vandenberg Air Force Base on a Delta II rocket. OCO-2 will be managed by NASA’s Jet Propulsion Laboratory in California.

Cloud-Aerosol Transport System (CATS) (Sept. 12): This technology demonstration project will use lasers, in three wavelengths, to examine tiny particles borne into the atmosphere from phenomena such as pollution, smoke, dust and volcanoes. “These aerosol particles pose human health risks at ground level and influence global climate through their impact on cloud cover and solar radiation in Earth’s atmosphere,” NASA stated. This will also leave Earth aboard a SpaceX resupply flight from Cape Canaveral.

Soil Moisture Active Passive (SMAP) mission (November): Will check out the moisture level of soil, with the aim of refining “predictions of agricultural productivity, weather and climate,” NASA stated. Also managed by JPL, this satellite will spend its time in an almost-polar “sun-synchronous” orbit that keeps the sun’s illumination below constant during SMAP’s turns around the Earth. SMAP will launch from Vandenberg on a Delta II rocket.

Source: NASA