Scientists hope Japanese probe can answer questions about planet Venus

By Kenneth Chang

Venus is not a placid paradise — that much we know. In addition to searing surface temperatures, wind in the upper atmosphere howls as fast as 250 mph, carrying clouds around the planet once every four days.

Yet Venus itself spins very slowly: one rotation every 243 Earth days — in the wrong direction, no less, opposite to almost every other body in the solar system.

On the whole, the atmosphere on Earth rotates about the same speed as the planet. So why does the air on slow-spinning Venus speed around so much faster than the planet itself?

The Japanese space probe Akatsuki, now in orbit around Venus, seeks to solve the mystery of so-called super-rotation.

That is not just an idle trivia question for planetary scientists. Computer models of our own weather fail when applied to Venus, and knowledge of the planet’s workings could better our understanding of Earth’s.

‘‘We don’t know what is the missing point in meteorology,’’ said Masato Nakamura, Akatsuki’s project manager.

In recent years, Venus has been a backwater of planetary exploration, even though it is much closer in size to Earth than is Mars. For a long time, scientists imagined there could be a habitable tropical paradise beneath Venus’ thick clouds.

In the late 1950s, intense thermal emissions, measured by a radio telescope on Earth, told a different story. Venus broils.

The average surface temperature is more than 850 degrees — an extreme demonstration of the heat-trapping prowess of carbon dioxide, the primary constituent of the Venusian atmosphere. Clouds of sulfuric acid make it an even less appealing place to visit.

In the 1990s, NASA’s Magellan spacecraft precisely mapped the topography of Venus through radar. Except for a few flybys by spacecraft on the way to somewhere else, NASA has not returned to Venus, although the agency is considering two modest proposals.

A European mission, Venus Express, studied the planet from 2006 to 2014, discovering among other things a frigid layer of atmosphere, minus 280 degrees Fahrenheit at an altitude of 75 miles, sandwiched between two warmer layers.

But now Akatsuki, which entered orbit last December, has begun its work. Takehiko Satoh, one of the mission scientists, said that one of ‘‘the most exciting, most surprising results’’ so far came almost immediately after the spacecraft arrived.

The camera that captures long-wavelength infrared light from the cloud tops discovered an arc-shaped white streak that stretched 6,000 miles from nearly the south pole to nearly the north pole.

Curiously, this giant atmospheric feature does not move with the atmosphere. ‘‘It seems to be fixed to the ground,” Satoh said.

The arc sits above Aphrodite Terra, a highland region about the size of Africa that rises up nearly 3 miles from the surface. Scientists working on data from the Venus Express reported a similar finding in July.The small spacecraft — the main body is a box a bit bigger than a refrigerator — carries five cameras, collecting light at different wavelengths to monitor the Venusian atmosphere at different altitudes.

In another experiment, scientists will observe how the radio signal from the spacecraft to Earth is distorted when it passes through the atmosphere. That will reveal temperature, abundance of sulfuric acid vapor and other properties. By observing the atmosphere at different altitudes, they can detect wavelike features that rise and fall, like blobs in a lava lamp.That Akatsuki, which means ‘‘dawn’’ in Japanese, is there at all is the result of ingenuity and perseverance.

It launched in May 2010 and arrived at Venus seven months later. But when its main engine failed to fire properly, it sailed right past the planet. ‘‘It was a very sad moment,’’ Satoh said.

Within a day, Satoh said, calculations indicated that in six years, Akatsuki, in orbit around the sun instead of Venus, could meet up with Venus again. But it was not clear the spacecraft still would be able to slow down and enter orbit.

An investigation found that a valve in the engine had leaked, leading to the formation of salts that fused it shut. The engine, as it fired, had overheated beyond repair.

Akatsuki still had the maneuvering thrusters that were to be used after it entered orbit. They were not as powerful as the broken engine, but they could apply enough force to slow it down enough so that Venus’ gravity could capture it.The Akatsuki’s orbit is different from the one originally envisioned. Instead of being synchronized to the spinning atmosphere, which would have allowed scientists to better track small changes, the spacecraft now loops around Venus in a large elliptical orbit.

That provides different benefits. Instead of intently staring at one spot, seeing the smallest changes, scientists are now able to see what happens on a global scale, although they will miss some of the details.

Akatsuki is to continue operating until at least April 2018, depending on how much fuel it has left. ‘‘We know at least we have one kilogram of fuel,’’ said Nakamura, likening the uncertainty to an imprecise fuel gauge in a car.

If it turns out that Akatsuki has more, the spacecraft could continue operating for perhaps up to six years, he said.

 


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Japan’s Akatsuki probe enters Venus’s orbit after floating through space for five years

By Rick Stella

After spending the last five years essentially lost in space, the Japanese probe Akatsuki fired up its engines this last weekend in hopes of finally entering the orbit of Venus. Though the craft previously reached Earth’s sister back in December of 2010, a faulty engine valve failed to propel the craft fast enough to catch the planet’s orbit, effectively closing its window of opportunity. Now, five years later, engineers at the Japanese Aerospace Exploration Agency (JAXA) confirmed the wayward Akatsuki spacecraft is now officially orbiting Venus.

During Akatsuki’s 2010 attempt, instead of positioning itself to fly into Venus’s elliptical equatorial orbit, the spacecraft’s malfunctioning engine’s prevented it from properly braking. Falling fuel pressure and a decrease in thrust improperly positioned the craft and before long, Akatsuki’s on-board fault protection shut the engine down to prevent complete failure. Once this happened, the probe flew right past Venus without catching the orbit.

Artist rendition of the Akatsuki orbiting Venus

Artist rendition of the Akatsuki orbiting Venus

To make matters worse, Akatsuki was completely covered by Venus during its engine burn meaning communication was non-existent with Earth during the attempt. Because of this, JAXA was unable to see exactly what happened until reading the probe’s recorded telemetry dataafter it had a go at entering the orbit of Venus. Lucky for the team behind Akatsuki, it became apparent a rare second chance would avail itself in the future; unfortunately, this second chance was five years away.

Opportunistic and hopeful, JAXA patiently waited five years for its second crack at Venus and, triumphantly, the agency prevailed. By making use of a set of small thrusters aboard the Akatsuki, engineers were able to slightly alter the probe’s trajectory so it could be pulled in by the gravity of Venus. Though the new orbit of the craft is slightly off what JAXA originally intended, the crew couldn’t help but get excited at Akatsuki’s renewed mission.

“We had a perfect operation,” exclaimed Masato Nakamura, JAXA’s project manager. “We have to wait another two days to confirm the orbit. I am very optimistic. It is important to believe in success!”

Now that it can examine Venus as it originally intended, JAXA intends to study the planet’s atmosphere while Akatsuki orbits at speeds of up to 186 miles per hour. They say patience is a virtue, but in the case of JAXA and its revitalized Akatsuki spacecraft, patience was absolutely essential.

Why Japan’s mission to Venus has been so full of drama

 

Russia, US could collaborate on mission to Venus

 

Jet Propulsion Lab/NASA/AP/FileView CaptionAbout video adsView Caption

After a pause following Russia’s annexation of Crimea, NASA and Russia’s space agency have resumed talks about the proposed Venera-D mission, which would orbit and land on Earth’s closest neighbor.

What Presidents Barack Obama and Vladimir Putin were discussing in that huddle at the G20 Summit earlier this week will likely remain a secret for some time. But could they have been talking about Venus?

While brinksmanship simmers over targeting the Islamic State in Syria and over the Kremlin’s actions in Ukraine, NASA has reportedly “resumed discussions” in October with Russia about a possible joint robot-led mission to Venus in the late 2020s, Spaceflight Now reports. The annexation of Crimea had put the potential venture on hold, though cooperation with the International Space Station continued, scientists involved in the talks said.

So far, NASA has only committed to a one-year feasibility study, which will culminate in a report for top officials in NASA and in Russia’s Moscow-based Space Research Institute (IKI). From there, officials will decide whether to pursue a cooperative mission to Venus, said Rob Landis, a program executive at NASA Headquarters, on Oct. 27, speaking from the Venus Exploration Analysis Group meeting in Washington.
The so-called “joint science definition team” reportedly convened in Moscow from Oct. 5-8, and scientists have slated two more in-person talks in Russia over the next year.
Scientists from the Russia’s IKI are heading up Venera-D, which is being considered as a chance to both orbit and land on Earth’s closest neighbor. NASA and IKI are also looking into whether the mission can accommodate a balloon that could to take wind and climate measurements from Venus’s scorching atmosphere.

Russia has a storied past with Venus, while for the US, this feasibility study comes as a new distraction from America’s first planetary love: Mars.

After nine failed tries at launching probes to Venus beginning in 1961, the Soviet Union’s Venera 7 landed successfully on the planet in 1970 – marking the first successful landing and communication from another planet. The subsequent Venera 8, 9, and 10 probes also all landed safely, with number 9 returning the first photos of the Venusian surface, Ars Technica reports.

With the Venera-D mission, which Russia first began planning in 2004, Russia aspires to land a more durable spacecraft on the surface of Venus, which is a hostile environment in the best of circumstances. The “D” in the mission stands for “dolgozhivushaya,” which means long-lasting. Venus’s average surface temperature can top 860 degrees Fahrenheit, and surface pressure is 92 times what it is on Earth.
IKI Director Lev Zelyony told Russian news Interfax that a joint flight will be possible after 2025.

By teaming up with NASA, Russia reportedly hopes to split the cost burden. NASA, for its part, has identified research objectives that an orbit and possible landing may accomplish. The agency’s Venus analysis group says its goal is to figure out how Venus diverged so dramatically from Earth, and relatedly, to further understand the “formation, evolution, and climate history on Venus.”

“We made a lot of progress,” said David Senske, a scientist at NASA’s Jet Propulsion Laboratory who is the US co-chair of the Venera-D science definition team. “We heard a lot about what they had in mind. We’ve been told this is an IKI/Roscosmos endeavor, so they’re in the driver’s seat.”

NASA and IKI have a deadline: The joint team’s report is due Sept. 30, 2016. Then a decision will be made as to whether a Russia-US mission to Venus is a go.

How Long Does It Take to Get to Mars?

Mars at its closest point to Earth in 2003

 

Mars is the fourth planet from the sun, and the second closest to Earth (Venus is the closest). But the distance between the two planets is constantly changing as they travel around the sun.

In theory, the closest that Earth and Mars would approach each other would be when Mars is at its closest point to the sun (perihelion) and Earth is at its farthest (aphelion). This would put the planets only 33.9 million miles (54.6 million kilometers) apart. However, this has never happened in recorded history. The closest approach of the two planets occurred in 2003, when they were only 34.8 million miles (56 million km) apart.

The two planets are farthest apart when they are both at their farthest from the sun, on opposite sides of the star. At this point, they can be 250 million miles (401 million km) apart.

The average distance between the two planets is 140 million miles (225 million km).

The speed of light

Light travels at approximately 186,282 miles per second (299,792 km per second). Therefore, a light shining from the surface of Mars would take the following amount of time to reach Earth (or vice versa):

  • Closest approach: 182 seconds, or just over 3 minutes
  • Farthest approach: 1,342 seconds, or just over 22 minutes
  • On average: 751 seconds, or just over 12.5 minutes

Fastest spacecraft so far

The fastest spacecraft launched from Earth was NASA’s New Horizons mission, which is en route to Pluto. In January 2006, the probe left Earth at 36,000 mph (58,000 kph). The time it would take such a probe to get to Mars would be:

  • Closest approach: 942 hours (39 days)
  • Farthest approach: 6,944 hours (289 days)
  • On average: 3,888 hours (162 days

But then things get complicated …

Of course, the problem with the previous calculations is that they measure distance between the two planets as a straight line. Traveling through the farthest passing of Earth and Mars would involve a trip directly through the sun, while spacecraft must of necessity move in orbit around the solar system’s star.

Although this isn’t a problem for the closest approach, when the planets are on the same side of the sun, another problem exists. The numbers also assume that the two planets remain at a constant distance; that is, when a probe is launched from Earth while the two planets are at the closest approach, Mars would remain the same distance away over the course of the 39 days it took the probe to travel. [Countdown: The Boldest Mars Missions in History]

In reality, however, the planets are continuously moving in their orbits around the sun. Engineers must calculate the ideal orbits for sending a spacecraft from Earth to Mars. Their numbers factor in not only distance but fuel efficiency. Like throwing a dart at a moving target, they must calculate where the planet will be when the spacecraft arrives, not where it is when it leaves Earth. Spaceships must also decelerate to enter orbit around a new planet to avoid overshooting it.

How long it takes to reach Mars depends on where in their orbits the two planets lie when a mission is launched. It also depends on the technological developments of propulsion systems.

Here is a list of how long it took several historical missions to reach the red planet. Their launch dates are included for perspective.

  • Mariner 4, the first spacecraft to go to Mars (1964 flyby): 228 days
  • Mariner 6 (1969 flyby): 155 days
  • Mariner 7 (1969 flyby): 128 days
  • Mariner 9, the first spacecraft to orbit Mars (1971): 168 days
  • Viking 1, the first U.S. craft to land on Mars (1975): 304 days
  • Viking 2 Orbiter/Lander (1975): 333 days
  • Mars Global Surveyor (1996): 308 days
  • Mars Pathfinder (1996): 212 days
  • Mars Odyssey (2001):  200 days
  • Mars Express Orbiter (2003): 201 days
  • Mars Reconnaissance Orbiter (2005): 210 days
  • Mars Science Laboratory (2011): 254 days