VEXAG meeting outlines plans for Venus exploration

Michael Cole

While Mars exploration and future human missions to Mars consume much of NASA’s energy and steal most of the space-related headlines, plans for the exploration of our other nearest planet are continuing as well.

The 13th meeting of the Venus Exploration Analysis Group (VEXAG ) was held in Washington D.C. last week to share the latest Venus science discoveries and review current proposals for upcoming Venus exploration missions.

“We serve as a conduit between the scientific community and NASA headquarters,” said Lori Glaze, current chair of VEXAG. “We provide some unity, consensus, and input to NASA that basically says where the science community thinks the most important questions are.”

VEXAG consists of a chair and five focus groups assembled from NASA centers and university scientific programs throughout the country. VEXAG is chartered by NASA’s Solar System Exploration Division and reports its findings to NASA.

Meeting attendees heard a report from ESA’s Hakam Svedhem on the conclusion of the Venus Express mission. Venus Express ended its eight-year mission in December 2014, after exhausting its propellant in a final effort to raise its orbit. It had far exceeded its original mission plan and duration, yielding a wealth of new data that Svedhem said will be analyzed for years to come.

Svedhem highlighted the spacecraft’s comprehensive study of the planet’s ionosphere and atmosphere. These observations have hinted at the existence of lava flows that may have occurred within the last few million years, suggesting that the planet is still geologically active today. Such observations are causing planetary scientists to consider rethinking their ideas about the geophysics of Venus.

Project scientist Takeshi Imamura of the Japan Aerospace Exploration Agency (JAXA), reported on the upcoming events of the Akatsuki, or Venus Climate Orbiter mission. Akatsuki was scheduled to enter orbit around Venus in December of 2010, but it flew by the planet when the spacecraft’s main engine failed during its orbital insertion burn. It has been orbiting the Sun since that time, but Imamura reported that JAXA is now preparing to make a second try at entering orbit around Venus on Dec. 7.

The orbital-insertion maneuver will be made with attitude control thrusters, due to the malfunctioned main engine. Imamura also reported that they dumped most of the dead main engine’s fuel, so it will take less energy from the thrusters to put it into orbit. If the maneuver is successful, Akatsuki will go into a highly elliptical orbit around Venus. From this orbit, the spacecraft will study the planet’s clouds, air circulation, and other atmospheric characteristics.

“We’ll be able to recover that mission,” said VEXAG chair Lori Glaze, “and hopefully recover a lot of the science it was going to do.”

Dave Senske of the Venus Science and Technology Definition Team at the Jet Propulsion Laboratory (JPL) presented a report on ongoing US-Russian cooperation on the Russian space program’s Venera-D mission.

“The D is Russian for long life,” Senske explained, meaning that the Russian spacecraft designers hope to create a spacecraft which can last longer than the roughly two hours that previous Russian Venera and Vega landers managed to transmit data from the planet’s surface.

“There are incredibly compelling science questions to understand how the surface of Venus formed, the variability in composition of the rock types, etc.,” Senske said. “What drives the atmosphere? What drives the super-rotation of the atmosphere? Although there have been significant accomplishments from the European Venus Express, there are a lot of questions left to be answered. Especially what we can tease out by getting to the surface. But getting to the surface is a tough nut to crack.”

With temperatures in excess of 860 degrees Fahrenheit (460 degrees Celsius), which is hot enough to melt lead, and pressures of 91 bar, equal to the pressure at about one mile beneath the ocean, Venus is indeed one of the most inhospitable places in the solar system.

“Because Venus is so hard in terms of getting into the atmosphere and down to the surface,” Senske said, “a joint international US/Russia mission may potentially bear some fruit.”

The Venera-D concept is made up of an orbiter and a lander. The orbiter will assess the atmospheric composition and a lander very similar to the Vega lander from the late 1980s, with more capable instruments, will make more high fidelity observations of the surface.

“We want to start to tease out how a planet that’s the same size as the Earth in roughly the same place in the solar system is so different, and geologically has a lack of plate tectonics,” Senske said. “We want to find out these things. What’s out nearest neighbor have to say?”

The hope of Senske and his Science and Technology Definition Team is to find commonality in the science goals of the Russian program, and those outlined for Venus in the most recent Planetary Science Decadal Survey.

“We want to find out what capabilities [the Russians] have, if they go forward with this,” Senske said, “to accomplish some of the mutual science goals that we identified in the Decadal Survey. We’re looking at the goals and objectives from both VEXAG and the Decadal Survey, and we’re literally in the process of cross-correlating those relative to the Venera-D concept that the Russians would like to move forward with. We want to find areas that are ripe for answering the questions that are the high priority Venus VEXAG/decadal-survey goals.”

One of the most important segments of last week’s VEXAG meeting were the presentations on the two Discovery class mission proposal finalists for Venus.

“There was a competition last year for a Discovery-class mission,” Glaze said. “There were twenty-seven proposals submitted, five were selected for phase A study. Two of those five proposals were Venus missions. Phase A means NASA provides funding, $3 million, for a 9-month concept study. This is to mature the design concept and to do a higher fidelity cost estimate of the mission.”

The first mission proposal presentation was by JPL’s Suzanne Smrekar, principal investigator for the VERITAS mission. VERITAS stands for Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy mission. It is an orbiter mission designed to produce global high-resolution topography and imaging of the surface of Venus, and to create the planet’s first deformation and global surface composition maps.

According to Smrekar, the overarching question VERITAS seeks to answer is “How Earth-like is Venus?” The mission design seeks to answer that question by revealing Venus’ geologic history, determining how geologically active it is, and searching for evidence of past and current water.

The second Venus mission proposal was presented by VEXAG chair Lori Glaze, who is Goddard Spaceflight Center’s principal investigator for the DAVINCI mission, the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging spacecraft. DAVINCI is an atmospheric descent craft that would study the chemical composition of Venus’ atmosphere during a 63-minute descent. These observations could answer questions that Venus scientists have considered high priorities for many years, such as determining if there are currently active volcanoes on the surface of Venus. This atmospheric data could also reveal how the surface of the planet, in its environment of extreme heat and tremendously high pressure, interacts with the atmosphere of the planet.

VEXAG members do not make recommendations about the two mission proposals.

“The review process is completely independent of VEXAG,” Glaze said. “That’s done with a peer review. They’ve already conducted the science peer review and the step 1 technical review and now they’ll do the step 2 review. There’s a completely separate panel that will do all those reviews, and then that panel will make recommendations to NASA headquarters as far as which proposal should be selected for flight.”

“What we provide are findings,” Glaze added, “and each finding generally encourages the Science Mission Directorate or the Planetary Science Division to invest in new technologies for this or that, or to invest in supporting an upcoming workshop that furthers the science goals we’ve identified.”

More new proposals for missions to Venus will likely be coming next year, as a competition for a New Frontiers class mission will open in February.

“There is a prescribed set of objectives for that New Frontiers class Venus mission, the Venus In Situ Explorer, and it’s defined in the Planetary Decadal Survey,” Glaze said. “I expect there will be at least two or three concepts submitted to that competition. There’s also a competition in Europe coming up in the coming year for their moderate M-class mission, and I am aware that there is at least one Venus concept being developed by the Europeans as well to be submitted to ESA.”

“We would love to see a Flagship class mission to Venus, but at the moment it’s not at the top of the decadal survey list,” Glaze said. “But maybe in the next decadal survey there will be.”