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Deep Space Digest – August 5

Venus Express gets a boost, Curiosity lives a hard rock lifestyle, Opportunity sets a record, Rosetta prepares to orbit a comet, and Cassini studies Titan.

Apologies for the late update this week.

In the News:

Venus Express

On July 25th, Venus Express performed the last of its orbit-raising burns, which will extend the life of the probe for several months following the successful aerobraking campaign that began in late May and ended on July 11. Prior to the aerobraking campaign, Venus Express was in a 250×66000 km orbit that took 24 hours to complete; the probe is now in a 22 hour 24 minute orbit that measures 460x63000km. According to an ESA blog post, this new orbit is expected to keep Venus Express from falling into Venus’s atmosphere until at least December.

Time since launch: 3193 days
Time elapsed time in Venus orbit: 2940 days
Light travel time to Earth: 13 minutes, 0 seconds


On August 4, NASA marked the second anniversary of Curiosity’s landing on Mars. In its two (Earth) years on Mars, Curiosity has needed to traverse difficult terrain which has proven damaging towards its aluminum wheels. The most recent encounter with rough terrain began a couple of weeks ago, when the rover needed to cross what is known as “caprock terrain” in order to get to a smoother route. In caprock terrain, soft sediments are eroded by wind to expose harder bedrock underneath. The erosion also sculpts the bedrock into points that can easily pierce the rover’s wheels.

Fortunately, Curiosity has made it across this region of caprock (named Zabriskie Plateau) with little further damage to its wheels. According to Curiosity Project Manager Jim Erickson, “The wheels took some damage getting across Zabriskie Plateau, but it’s less than I expected from the amount of hard, sharp rocks embedded there. The rover drivers showed that they’re up to the task of getting around the really bad rocks. There will still be rough patches ahead. We didn’t imagine prior to landing that we would see this kind of challenge to the vehicle, but we’re handling it.”

Curiosity currently sits about 3km (2 mi) from the foot of Mt. Sharp, but outcrops of the lowest rock layers that make up the mountain occur less than 500m (1/3 mi) from Curiosity’s current position. Curiosity should reach the outcrop, named “Pahrump Hills” in the next week or so.

Time since launch: 984 days
Total elapsed time on Mars: 709 sols (728 Earth days)
Light travel time to Earth: 10 minutes, 6 seconds
Total roving distance: 9.00km (5.59 miles)


Opportunity has finished working at one outcrop of clay minerals spotted by the Mars Reconnaissance Orbiter, and has begun to move on to the next area of potential clay minerals, dubbed “Marathon Valley”. On its way, Opportunity has been performing “touch and go” operations, in which it spends one sol analyzing a rock with its APXS spectrometer, then the next day driving to another target. During the “go” days, Opportunity completed several long drives, with the longest being a 100m drive on July 20 and a 99m drive on July 22.

A 48m drive on July 27 made Opportunity the most well-traveled extraterrestrial rover in history, edging out the record set by the Soviet Union’s Lunokhod 2 rover in 1973. Opportunity is still in good health, although flash memory resets occurred on July 15 and 19. The reset that occurred on July 15 took place during a drive, the first time that has happened.

Time since launch: 4049 days
Total elapsed time on Mars: 3744 sols (3846 Earth days)
Total roving distance: 40.28km (25.03 miles)
Light travel time to Earth: 10 minutes, 6 seconds



Rosetta is set to make history by becoming the first spacecraft to orbit a comet with an orbital insertion maneuver that will occur on August 6. The maneuver will be livestreamed from the ESA’s operations center in Darmstadt, Germany beginning at 10:30 CEST (4:30am EDT). Here is a great blog post by the ESA that details how Rosetta has approached the comet.

As Rosetta approaches, its navigational cameras have been returning increasingly good pictures of 67P/Churyumov-Gerasimenko. The most recent images of the comet were taken on August 3 from a distance of 300km, and show a wealth of detail on 67P’s surface. After orbital insertion, Rosetta will continue taking pictures of the comet from a preliminary mapping orbit of 100km in order to find a landing site for its Philae lander.

Time since launch: 3848 days
Current distance from 67P/Churyumov-Gerasimenko: ~300km (~185 miles)
Current distance from Earth: 404 million km (251 million miles); light travel time: 22 minutes 27 seconds



The highlight of this update period was a flyby of Titan on July 20 at a distance of 5103km (3170 mi). As it flew by the moon, Cassini watched as the Sun slipped behind Titan’s atmosphere over about an hour, followed later by the bright star Alpha Eridani. Both events were studied using the Ultraviolet Imaging Spectrometer (UVIS), Composite Infrared Spectrometer (CIRS), and Visible and Infrared Mapping Spectrometer (VIMS) instruments, which help build up a picture of the chemical layering in Titan’s atmosphere. During the flyby, Titan also looked for glints of sunlight reflecting off the surface of Kraken Mare, a large lake approximately the size of Lake Superior. As Cassini receded, it imaged Titan’s northern hemisphere, looking for convective clouds forming in the summer heat.

The Titan flyby also placed Cassini into the most inclined orbit of its mission, at 48 degrees to Saturn’s ring plane. Future flybys will begin to return Cassini’s orbit closer to Saturn’s ring plane to enable close flybys of Enceladus and Dione in late 2015. Cassini’s inclined orbit gives it a great view of Saturn’s ring system from above and below. On July 16, Cassini looked at known “propellers”, strands of material pulled out of Saturn’s rings by the gravity of small moonlets. Although the moonlets themselves (less than 500m across)  are invisible to Cassini, the propeller features they create make it possible to study how they change in size as they interact with the ring system. Another way to study Saturn’s rings is to watch as stars pass behind them, watching for dimming as light is absorbed by ring material. On the 16th and 17th, the VIMS instrument watched as the stars Vega and R Lyrae passed behind the rings. On the 18th, Cassini imaged a nearly empty area in Saturn’s rings, the Encke Gap, for 8 hours in order to make a time-lapse movie.

In addition to its ring studies, Cassini also looked at the tiny moon Ijiraq on July 26 and 28. Ijiraq, named for a creature in Inuit mythology that plays hide and seek, is a dark moon only ~10km in diameter that orbits Saturn nearly 11 million km away. Cassini also looked for emerging storms in Saturn’s atmosphere on July 25, as well as performed a yearly examination of Saturn’s magnetosphere with the UVIS instrument on July 29.

Time since launch: 6133 days
Total time at Saturn: 3689 days
Light travel time: 1 hour, 21 minutes


Other missions:


On August 3, NASA celebrated the 10 year anniversary of MESSENGER’s launch. In celebration, the MESSENGER team released a short video of Mercury’s surface as the spacecraft flew over the planet’s north pole on June 8. The video is a glimpse of the high-resolution images that MESSENGER will be capable of producing in its final year orbiting the planet.

Time since launch: 3654 days
Total elapsed time in Mercury orbit: 1237 days
Light travel time to Earth: 11 minutes, 1 second


Chang’e 3/Yutu

Time since launch: 249 days
Time since landing: 236 days



MAVEN finished its cruise-phase instrument checkouts on July 17. The probe was placed into hibernation in preparation for orbital insertion on September 22, 2014.

Time since launch: 261 days
Current distance from Mars: 12.7 million kilometers (7.9 million miles)
Current distance from Earth: 165 million kilometers (105 million miles); light travel time: 9 minutes, 27 seconds


Mars Orbiter Mission

ISRO celebrated the fact that their Mars Orbiter Mission had made it 75% of the way to Mars on July 4. So far, the success of the mission has led the Indian space agency to consider a follow-up mission to Mars between 2017 and 2020. India’s first Mars mission is currently en route to the Red Planet, where it will arrive on September 24, 2014.

Time since launch: 255 days
Current distance from Mars: 13.0 million kilometers (8.1 million miles)
Current distance from Earth: 165 million kilometers (105 million miles); light travel time: 9 minutes, 25 seconds



Currently en route to the asteroid Ceres, where it will arrive in February 2015.

Time since launch: 2492 days
Time since Vesta departure: 687 days
Current distance from Ceres: 7.0 million kilometers (4.3 million miles)
Current distance from Earth: 406 million kilometers (252 million miles); light travel time: 22 minutes 34 seconds



Currently en route to Jupiter, where it will arrive in August 2016.

Time since launch: 1092 days
Current distance from Jupiter: 325 million kilometers (202 million miles)
Current distance from Earth: 650 million kilometers (404 million miles); light travel time: 36 minutes, 10 seconds


New Horizons

New Horizons is now less than a year away from its flyby of Pluto, which will occur on July 14, 2015.

Time since launch: 3122 days
Current distance from Pluto: 408 million kilometers (253 million miles)
Current distance from Earth: 4.36 billion kilometers (2.71 billion miles); light travel time: 4 hours, 2 minutes


Voyager 1

Time since launch: 13,483 days
Current distance from Earth: 19.17 billion kilometers (11.91 billion miles); light travel time: 17 hours, 45 minutes


Voyager 2

Time since launch: 13,499 days
Current distance from Earth: 15.67 billion kilometers (9.74 billion miles); light travel time: 14 hours, 31 minutes

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About The Author
Justin Cowart
Justin Cowart is a geologist interested in Earth and Solar System history. As a geologist, he spends hist time looking at the ground, but in his free time he looks to the skies as an amateur astronomer.

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