Sunday, December 28, 2014

Earth Photos From The ISS Are Full of Surprises

One reason I love twitter, tweeting and tweeps is that I learn so much simply by doing something I enjoy. Hardly a day goes by that I don't learn something new. Here is today's discovery.

This morning, Sam Cristoforetti @AstroSamantha, who is currently aboard the International Space Station, tweeted a picture of the Hawaiian Island O'ahu with Honolulu clearly visible.

I retweeted this to my own timeline without noticing the odd coloration of the ocean at the top and at the left side of the picture, most likely because I initially saw a small version of it on my phone. 

Shortly thereafter, Frank Benson @mfbenson1 brought up this excellent question:

I took a second look at the picture and suggested we might be looking at some very thin, low cloud cover, since mud or sediment don't make much sense, given local geography. Clouds were my best guess, but since I didn't know for sure I included Peter Caltner @PC0101 in the conversation, who is a veritable fount of useful and factual information about pictures of Earth taken from the International Space Station. Turns out Frank and I had both guessed wrong:

Peter then tweeted a photo taken from the ISS that shows an example of extreme sun glint, so much so that the brightness 'wipes out' the colors of the land.

He added that glint pictures can be extremely useful, since they show coastal inlets and river courses better than aerial views. The ISS orbits at ca. 220 mi (350 km) above Earth.

Thanks, Peter, for this really cool lesson in orbital photography effects!

Thursday, December 25, 2014

Season's Greetings From Rosetta and Philae!

I had planned to publish this article tomorrow. Alas, @ESA_Rosetta tweeted an adorable Rosetta / Philae Christmas cartoon today that convinced me this article should have a December 25 publication date:

The European Space Agency's Rosetta mission to comet Churyumov-Gerasimenko (aka 67P) launched in 2004 and arrived at its destination earlier this year. One of the mission's first surprise findings came when Comet 67P - assumed to be potato-shaped - resolved to look more like a... rubber duck! Comet 67P is two-lobed, with one lobe distinctly smaller, giving it a familiar shape in human terms. Certainly, "the rubber duck comet" is a less challenging name to pronounce than "comet Churyumov-Gerasimenko!

On November 12, 2014, the Philae lander detached from the Rosetta spacecraft to perform the first comet landing in history. The maneuver was far from perfect - Philae's harpoons meant to anchor it to the comet surface did not fire, nor could the screws in Philae's feet deploy to secure the probe to the comet. As the lander touched down, it actually bounced back into space - not once, but twice, before landing on its side. Regardless, for the first time ever, human eyes are able to get a close-up look at an ancient celestial object in our solar system! 


Above is a full color image of Comet 67P/Churyumov-Gerasimenko that Rosetta took last August through red, blue and green filters. This is how the comet would appear to human eyes, revealing that it is... gray. When this picture was taken, Rosetta was about 120 km (75 mi) distant from Comet 67P, before Philae was deployed. The comet's uniformly gray appearance suggests that any water ice it contains is distributed more or less evenly throughout the comet's two lobes. If there were alternate patches of all-water ice or all-rock we would expect some areas of the comet surface to be brighter than others. The black areas are shadows caused by sunlight streaming across a surface full of steep cliffs and boulders.

Photo credit: ESA/Rosetta/NAVCAM

Most recent image of Comet 67P taken December 16 by Rosetta, orbiting the comet, with Philae on the surface.

Photo credit: ESA/Rosetta/Philae/CNES/FD 

Simulation of Philae on the surface of Comet 67P - Philae is wedged sideways between the base of a cliff and a large rock outcropping, with one of its legs stuck between rocks. After its initial comet touchdown, Philae bounced twice before coming to rest in its current position. Philae was meant to fire harpoons upon landing to anchor itself to the comet and deploy screws in its feet to secure itself in place during its trip around the sun.

Photo credit: ESA/Rosetta

These are Philae's 10 science instruments. It is currently unknown to which extent some or all of them can be used during the primary science mission. Philae is now in hibernation mode, as it is stuck in an area of the comet surface that gets only a few hours of sunlight per day - not enough to wake the probe from hibernation. This may change as the comet approaches the sun in coming months. If Philae can be roused from its deep sleep, we may yet obtain a treasure trove of data about what happens when comet 67P approaches perihelion.

For now, let's keep in mind that Philae has been functioning at only a fraction of its intended capacity and yet was already able to return an incredible set of never-before-seen comet data.

Photo credit: ESA/Rosetta/Philae/CIVA 

Philae's very first picture is a bit of a blur since the lander was bouncing at the time.

Photo credit: ESA/Rosetta/Philae/CIVA 

Comet close-up: Photo of the cliff right in front of Philae that is blocking its sunlight. The image reveals a number of fissures and fractures. The reflective glare on the rock is caused by the lander.

Credit: Rosetta/ESA

In addition to data that Philae may yet collect on the comet surface, the Rosetta spacecraft continues to accompany 67P and Philae as they journey towards the inner solar system. Rosetta will orbit the two-lobed comet at altitudes of as little as 6.5 km (4 mi). Already Rosetta has returned spectacular images such as the above - cometary cliff faces that are more than half a mile high (ca.1 km). The whole comet is about 4.5 km (2.8 mi) wide, measured duck head to duck tail.

Tuesday, December 16, 2014

SpaceX's Jan. 10 CRS-5 Launch Includes Precision-Landing Upper Rocket Stage On Barge

Update - January 8: SpaceX's CRS-5 resupply mission to the ISS has been postponed to Saturday, January 10, 1:47 a.m. PST (10:47 CET) - a weekend night launch. I'm sure other West Coast night owls like myself will stay awake to watch and live tweet the launch, given the historic nature of this mission. NASA TV will provide live coverage, starting at 12:30 a.m. PST (9:30 CET). Details about this mission are below the Update sections.

Update - January 6: Today's launch attempt was scrubbed at the last minute due to a problem with an actuator assembly, a part of the rocket's second stage engine steering system. The next launch attempt is scheduled for Friday, January 9, at 2:09 a.m. PST (11:09 CET) - an almost reasonable time for us West Coast night owls. SpaceX is characteristically stingy with details; Elon Musk posted this tweet today:

Update - December 18: Due to issues with a static fire test this week, SpaceX has moved the launch date to January 6, 2015, at 3:18 a.m. PST (12:18 CET).

Delayed multiple times since September, SpaceX's cargo delivery to the International Space Station is scheduled for January 10, 1:47 a.m. PST (10:47 CET), launching a Dragon cargo capsule atop a Falcon 9 rocket from pad SLC-40 at Cape Canaveral. This mission will be the private space company's fifth cargo delivery to the ISS under NASA's Commercial Resupply Services contract. 

The mission is named CRS-5 and here is its patch. I like how the launch state of Florida is marked in a lighter blue color. Naturally, the traditional SpaceX clover leaf is there as well. What I like most about it is that Falcon 9 is practically bursting out of the confines of this beautiful patch, conveying anticipation, excitement and confidence in what's ahead. The Dragon capsule on the right has already found a way to escape its patch boundaries, but, hey, that lucky capsule is going to the International Space Station, so Dragon's impatience is quite understandable!


For SpaceX, CRS-5 is quite a bit more than another supply run to the ISS, as the company will further test re-usability functions and performance of its flagship Falcon 9 rocket. From its inception, SpaceX has aimed to make spaceflight more affordable and accessible. Reusable rocket stages are a crucial factor in the quest to develop rockets that are significantly cheaper to fly than their single-use counterparts. Notice the upside down V-shaped structures on the rocket in the patch - or, from a Trekkie's perspective, the Star Trek emblem-shaped structures affixed to this Falcon 9 stage. These are Falcon 9's landing legs for attempting a soft landing on a spaceport barge.

On a mission earlier this year, SpaceX began post-launch re-usability testing by guiding the Falcon 9's rocket stage to hover upright above the ocean for a few seconds before it tipped over sideways into the water. SpaceX uses a combination of landing legs, grid fins, retro rockets and stabilizing technologies, enabling Falcon 9's upper stage to perform a precision soft landing on water and eventually on land.

This time, Falcon 9's upper stage is expected to land on an autonomous spaceport drone ship. On twitter, SpaceX CEO Elon Musk gave us a glimpse of what to expect on January 10 - a historic milestone never before achieved: precisely land and recover a rocket that is intact and reusable, without the need to fish it out of the water.

Saturday, December 13, 2014

Year of the Dwarf Planets: Ceres 2015

In 2015, Pluto won't be the only dwarf planet that will receive a visit from an electronic ambassador. NASA's Dawn mission is currently on its way to Ceres.

Dawn was launched in 2007 to study the two largest celestial objects in our solar system's asteroid belt: asteroid Vesta and dwarf planet Ceres. Dawn studied Vesta from July 2011 to September 2012 and is now headed for Ceres. The dwarf planet is of particular interest since it is the asteroid belt's largest object, accounting for 25% of its total mass. In addition, Ceres is differentiated, with a rocky core, like Earth and Mars, and a water ice layer below a thin outer crust, like some of the moons of the gas giants Saturn and Jupiter. 

In January 2014, using observations from the Herschel Space Observatory, astronomers discovered that Ceres was releasing water vapor into space from two points near its equator, at a rate of about 5 kg (11 lbs) / second. At the time these observations were made, the 950-km-wide (590 mi) dwarf planet was closest to the sun (perihelion) during its 4.5-year-orbit around the sun. This was an unexpected and exciting finding. The presence of water on Ceres raises the possibility of alien life. In addition, water vapor plumes have never been observed escaping from an asteroid belt object. 

Ceres thus poses a number of intriguing questions. In coming months, scientists will likely be able to answer many of them.

Image credit: NASA

Artist's impression of dwarf planet Ceres outgassing water vapor into space from two sources near its equator. This suggests the presence of water and the possibility of alien life.

Image credit: William K. Hartmann Courtesy of UCLA

Artist's rendition of Dawn in the asteroid belt between Mars and Jupiter, marking the boundary between our solar system's inner and outer planets. Vesta is the largest, potato-shaped asteroid on the left, and the dwarf planet Ceres - almost shperical in shape - is at the right.

Image credit: NASA

Ceres is a dwarf planet in the asteroid belt with a rocky inner core, a trait it shares with inner planets like Mars and Earth, and a sub-surface water-ice layer, a feature it has in common with some of the moons of the outer planet gas giants Saturn and Jupiter.

This is the highest resolution image we have of Ceres to date, taken by the Hubble Space Telescope. Dawn will arrive at Ceres in late March / early April 2015 and start to return images with a higher resolution than the above in about six weeks. That event will mark the first time humans will get a close-up look at a dwarf planet. New Horizons will arrive at Pluto several months later. The differences and similarities between the two dwarf planets will provide a wealth of information about the formation of our solar system. 

Dawn will initially orbit Ceres at an altitude of 13,500 km (8,400 mi), and descend to about 1,500 km (950 mi) in August 2015 to resolve Ceres' surface in 3D. Dawn's closest passes to the surface will be at an altitude of 375 km (230 mi) in November 2015, where the craft will remain for three months.

Sunday, December 7, 2014

New Horizons: All Eyes On Pluto in 2015

On December 6, New Horizons awoke from hibernation for the final time. This amazing outer solar system probe was launched in 2006 and has traversed 3 billion miles. New Horizons is going further than any planetary probe has gone before; only the two Voyagers - designed to leave the solar system - have traveled further from our home planet. The spacecraft is also zooming fast through space - at a clip that equals traveling from Los Angeles to New York every five minutes, since 2006.

Yesterday New Horizons woke up for the 18th and final time. The probe spent most of its journey in hibernation mode, only waking up periodically for instrument and status checks. Now that New Horizons is closing in on the Plutonian system, we can expect to see the dwarf planet and its moons with ever increasing resolution. New Horizons will have its closest encounter with Pluto in July 2015. 

Data sent from Pluto won't arrive at Earth instantaneously. It takes 4.5 hours for the signal to traverse 3 billion miles through the vacuum of space to be received on Earth.

 Image credit: The Planetary Society

Below is an artist's rendering of New Horizons approaching Pluto and its moons. The dwarf planet at the outer edges of our solar system is still the least well known to us here on Earth. Having lost its status as a full planet not too long ago, Pluto is now likely to present us with spectacular images of its surface and a wealth of knowledge. In a way, going to Pluto is like discovering what an exo-planet looks like. We can't see its surface directly, and, until now, we could only guess what its surface may look like. New Horizons will also be able to discern the presence of subsurface oceans similar to those on icy moons further inside the solar system, volcanic activity like we found on Io, or plumes that vent into space as we see it on Enceladus.

One of the questions mission scientists are eager to answer is whether or not Pluto and its current features are primitive - unchanged since the dawn of our solar system - or the result of activity over time, such us tidal heating or subsurface oceans. 

New Horizons' science instruments will also explore Pluto's night side, search for rings, study the atmosphere, look for dust, plasma and hazes, and collect data that will tell us if Pluto has mountains, fault lines, chasms and other geological features. 

 Image credit: NASA

This is a Hubble telescope image of Pluto and its five moons. Charon is the largest and was discovered in 1978. Two of Pluto's smaller moons, Kerberos and Styx weren't discovered until 2011 and 2012, respectively. This poses a unique challenge for New Horizons scientists: Completing science missions at Pluto and Charon while taking into account two moons that were not known to exist when New Horizons launched in 2006.                     

 Image credit: NASA / Hubble

Below is a Hubble telescope image of Pluto and three of its moons. This is the highest resolution image of Pluto and its moons that we have to date. As New Horizons approaches Pluto in coming months, the spacecraft will start to return images that will be better than this in early May 2015. New Horizons scientists have named this threshold "BTH" - Better Than Hubble. After that point, the craft will return images with increasingly finer resolution until its closest encounter with the dwarf planet in July 2015. At its closest approach, New Horizons' camera will resolve Pluto's surface at about 70-80 m / pixel.

 Image credit: NASA / Hubble

New Horizons' mission may not end after visiting Pluto and Charon. NASA scientists are working to secure funding for extending the spacecraft's mission. It can use Pluto's gravity to slingshot out into the Kuiper Belt and examine a Kuiper Belt Object up close. Two possible target objects have already been selected. A close-up look at a KBO is particularly interesting because it will help us understand the nature and state of the very early solar system, long before planets had time to form. KBOs are thought to have changed very little in the billions of years since the formation of the solar system as we know it.