June 20, 2021

NASA selects two robotic missions to Venus for launch in late 2020s


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The northern hemisphere is displayed in this global view of the surface of Venus as seen by NASA Magellan spacecraft. Credit: NASA/JPL

NASA has selected two robotic missions for launch to Venus around 2029, the U.S. space agency’s first spacecraft in more than 30 years dedicated to exploring the hellishly hot second planet from the sun.

The two winning proposals — named DAVINCI+ and VERITAS — won a competition run by NASA to select the next projects for development under the agency’s Discovery program, a line of cost-capped planetary science missions.

“Congratulations to the teams behind NASA’s two planetary science missions: VERITAS — “truth” — and DAVINCI+,” said NASA Administrator Bill Nelson in the June 2 announcement. “These two sister missions both aim to understand how Venus became an inferno-like world capable of melting lead at the surface. They will offer the entire science community the chance to investigate a planet we haven’t been to in more than 30 years.”

NASA’s last mission devoted to observing Venus was Magellan, which launched on a space shuttle in 1989 and arrived in orbit around the planet in 1990. Megallan mapped Venus’s surface using radar waves, which can pierce the planet’s thick clouds, to reveal the planet’s mountains and topography.

Since Magellan, several NASA spacecraft has sailed by Venus on the way to other planetary destinations, and Europe and Japan have sent orbiters to Venus.

Nelson said further study of Venus, sometimes called Earth’s twin, will help scientists understand how Earth and Venus diverged in their evolution throughout the solar system’s 4.5-billion-year history.

“In our solar system, of the rocky planets, there’s Mercury, the closest to the sun. It has no atmosphere,” Nelson said. “Then there’s Venus with an incredibly dense atmosphere, then there’s Earth with a habitable atmosphere, and then there’s Mars with an atmosphere that is just 1% of Earth’s. We hope the missions will further our understanding of how Earth evolved, and why it’s currently habitable when others in our solar system are not.”

Using a more sensitive radar instrument, VERITAS will update the topographic maps created by NASA’s Magellan spacecraft in the early 1990s, potentially revealing whether geologic processes such as volcanoes are currently active on the planet.

DAVINCI+ will send a small probe, measuring roughly 3 feet (1 meter) across, into the thick atmosphere of Venus. The instrumented craft will plunge into Venus’s carbon dioxide-rich atmosphere, deploy a parachute, and descend through cloud layers made of sulfuric acid before eventually landing on the surface.

“We’re revving up our planetary science program with intense exploration of a world that NASA hasn’t visited in over 30 years,” said Thomas Zurbuchen, NASA’s associate administrator for science. “Using cutting-edge technologies that NASA has developed and refined over many years of missions and technology programs, we’re ushering in a new decade of Venus to understand how an Earth-like planet can become a hothouse.

“Our goals are profound,” Zurbuchen said in a statement. “It is not just understanding the evolution of planets and habitability in our own solar system, but extending beyond these boundaries to exoplanets, an exciting and emerging area of research for NASA.”

VERITAS stands for the Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy mission. The development of VERITAS will be led at NASA’s Jet Propulsion Laboratory in Pasadena, California.

The DAVINCI+ mission, which stands for Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging – Plus, will be managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

NASA said the missions will launch in the 2028-2030 timeframe. Each mission will get approximately $500 million for development, excluding launch costs and international contributions.

In interviews with Spaceflight Now, the lead scientists for the VERITAS and DAVINCI+ missions said NASA has directed the teams to target launches in 2029, a schedule driven by budget availability.

“We’ve waited a long time for a U.S. mission to go back through the atmosphere of Venus, and we’re delighted to be that mission,” said Jim Garvin, chief scientist at Goddard and principal investigator for the DAVINCI+ mission. “So thanks to all fo the women and men that got us here. We can’t wait to go.”

“We’re just so thrilled to have this opportunity to go to Venus,” said Sue Smrekar, principal investigator for the VERITAS mission at JPL. “For me, it’s a lifelong dream. For many, it’s been a labor of love for a year, five years, 10 years. Many have been working on it for a long time.”

NASA selected the VERITAS and DAVINCI+ missions over two other finalists.

One of the candidates, the Io Volcano Observer, would have sent a spacecraft to orbit Jupiter and pass near the moon Io, the most volcanically active body in the solar system. The Trident mission proposal would have dispatched a probe to fly by Triton, the largest moon of Neptune, which harbors geyser-like plumes erupting from its icy surface.

But Venus, which NASA has bypassed in several recent mission selections, won support this time.

Data from DAVINCI+ will help scientists understand how the atmosphere of Venus formed and evolved, and help determine whether the planet — about the same size as Earth — ever had an ocean.

“The science is simple,” Garvin told Spaceflight Now. “Venus has a massive atmosphere. It’s layered, or stratified, and it records the history of billions of years of planetary evolution, which for Venus is still a mystery. It’s an enigmatic rocky planet with a big atmosphere. We think Venus likely harbored global oceans for billions of years. That’s the best modeling that we can get from what little we know.”

While Earth and Venus may have been similar billions of years ago, Venus’s super-dense atmosphere is now 90 times thicker than Earth’s. The sweltering blanket of carbon dioxide turns up the temperature at the surface to 900 degrees Fahrenheit (480 degrees Celsius).

“So what happened? What happened to the climate change? How does that couple through the crust and rocks? What does that do the clouds, which are thick and fascinating, and how does that work?” Garvin said.

Artist’s illustration of NASA’s DAVINCI+ mission at Venus, showing the atmospheric entry probe descending through Venus’s clouds to the surface. Credit: NASA/GSFC visualization and CI Labs Michael Lentz and colleagues

“We’re going to measure the history of water, other critical chemistries of carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, their cycles, from the top of the atmosphere to the surface,” Garvin said. “We’re going re-measure the critical state of the lower atmosphere, temperature and pressure. It’s super critical, so it’s not a true gas, or an ideal gas. We’ll measure that.”

DAVINCI+ was designed and proposed before scientists announced last year evidence of phosphine gas in the clouds of Venus, an indicator of possible life. Phosphine, made by combining a phosphorus atom with three hydrogen atoms, is only generated on Earth from microbes and industrial activity.

But some researchers have voiced doubts about the phosphine discovery. DAVINCI+ will be outfitted to make direct measurements of phosphine, if it is there.

The descent probe will be a titanium sphere housing a mass spectrometer and a tunable laser spectrometer to measure the composition of the atmosphere from top to bottom. The craft will also have instruments to measure pressures, temperatures, winds, and accelerations during descent, and a near-infrared camera system peering out the bottom of the probe will take pictures of the surface of Venus.

“Below the clouds, we’ll use a very high resolution new kind of descent imaging system that will not only take pictures but it will make images from which we can infer composition and topography,” Garvin said. “So we’re going to that all the way down from something like 90,000 feet (27.4 kilometers) to the surface, ever getting closer, and finally we’ll be taking images with resolution like if you were flying a drone over your backyard.”

The probe will be suspended under a parachute as it falls through Venus’s atmosphere. The entire descent will take about an hour, targeting an area of Venus called Alpha Regio, a mountainous region first discovered in the 1960s using Earth-based radar observations.

“We’re going to go into those mountains,” Garvin said. “They’ve never been seen at human scales. We’ll be seeing them, measuring them, and measuring the chemistry of the atmosphere above them. So all that will give us a storybook, an evolutionary history of Venus, and we’ll apply that forward across the solar system, but also to exoplanets (planets around other stars) we’ll be able to measure with the James Webb Space Telescope.”

The last U.S.-led mission to send a probe into the atmosphere of Venus was Pioneer Venus in 1978. The Soviet Union’s Vega missions were the last to plunge deep into Venus’s atmosphere in 1985.

The descent probe itself will be built in-house at NASA’s Goddard Space Flight Center, while Lockheed Martin will supply the aeroshell, heat shield, and a carrier spacecraft to ferry the entry vehicle from Earth to Venus, according to Garvin.

The carrier spacecraft will relay data from the DAVINCI+ descent probe back to Earth. The carrier will not enter orbit around Venus, but will fly by the planet on a trajectory to provide about an hour of solid communications with the entry vehicle.

If the descent probe safely reaches the surface, the mission could return some bonus data. But scientists have not committed to that as part of the DAVINCI+ primary mission.

“We get our own big radio communication system right there at Venus on a trajectory that gives us really favorable communications, a nice long arc that lasts up to an hour or so,” Garvin said. “In fact, if it survives surface impact, which we don’t know … we could potentially communicate for another 10 or 15 minutes because we would have the comm link. We don’t know if that will be possible, and it’s not part of our mission, but … we might have that opportunity.

“The spacecraft is thermally conditioned to operate for about an hour-and-a-half,” Garvin said. “Once it’s down in that hot environment, (the conditions) will eventually get to the point that the electronics of our primary four instruments will not be functional.”

The DAVINCI+ carrier spacecraft will have its own science instruments, including a suite of ultraviolet and near-infrared cameras to track cloud motion and measure thermal emissions from the surface.

A technology demonstration package on DAVINCI+ will test the Compact Ultraviolet to Visible Spectrometer, or CUVIS, instrument to study an unknown ultraviolet absorber in Venus’s atmosphere that absorbs up to half the incoming solar energy, NASA said.

According to Garvin, assuming DAVINCI+ launches in 2029, the mission will perform two flybys of Venus in 2030 before the returning to the planet in 2031 to release the descent probe.

Artist’s concept of the VERITAS spacecraft. Credit: NASA/JPL-Caltech

The other Venus mission, VERITAS, will carry a synthetic aperture radar instrument on an orbiting spacecraft to survey the planet’s surface over nearly the entire planet.

“Our goal is to really understand the geologic evolution of Venus, why it’s different from the Earth, and try to understand why Venus never developed plate tectonics,” said Smrekar, the lead scientist on the VERITAS mission. “How has that affected the evolution of its climate?

“We’re looking at the volcanic history trying to understand whether its craters were wiped out by catastrophic volcanism, or whether, or not there’s steady, perhaps even Earth-like quantities of volcanism happening today,” Smrekar said in an interview. “So we have a lot of different science investigations to follow up on, but our overall goal is to understand the big picture evolution of Venus, and why it’s so different from its twin planet.”

The VERITAS spacecraft will carry two instruments to Venus.

The primary payload is an X-band synthetic aperture radar to greatly improve the 3D topographic maps produced by the Magellan mission.

“It will create global maps of the surface, a topography map, that has 100 times the resolution of Magellan,” Smrekar said.

The radar on VERITAS will produce data with a vertical accuracy of about 16 feet, or 5 meters, and a horizontal resolution of about 100 feet, or 30 meters, on a global scale. About 25% of the surface of Venus will be mapped at about 50-foot, or 15-meter, resolution, according to Smrekar.

“We also do repeat passage interferometry, which will be our first for any planet beyond the Earth,” she said. “We basically take radar images separated by about seven months, and then look for deformation between the images.

“We could see volcanic deformations, such as a caldera inflating or deflating,” she said. “We could see faulting deformation. There are suggestions that the rifting features on Venus could be active, so we’ll be looking for deformation in those kinds of areas. And from (ESA’s) Venus Express, we got hints of recent volcanism as well, so we’ll check out those areas.”

A spectrometer on the VERITAS spacecraft will peer through clouds and measure the composition of Venus’s surface. The spectrometer will be tuned to detect iron, among other elements.

“So we’ll be able to do things like assess the theory, the hypothesis, that Venus has continent-like features,” Smrekar said. “It has these big high plateaus that are highly deformed and are believed to be low in iron content. If that hypothesis is correct, they’re basically fingerprints of past water because on the Earth, when continents form, it’s basically massive quantities of basalt melting in the presence of water. So they may be basically remnants from Venus’s wetter past.”

VERITAS will also look for thermal and chemical signatures of recent volcanic eruptions, and search for water that could be spewed out of Venus’s interior through volcanoes. If there’s evidence of that, it would indicate there must be significant amounts of water in the interior of Venus.

The mission will also help refine estimates of the size of Venus’s core, Smrekar said.

She said the VERITAS and DAVINCI+ missions, while developed by separate teams, are “very complementary.”

“VERITAS provides the global mapping and context for any of the near-surface measurements that DAVINCI+ will make,” Smrekar said. “They will take imaging data as they descend below the cloud deck, so to have those images of areas that we have radar data for will be great ground truth for the radar. We can also provide to them targeting for the most exciting scientific targets.”

The spacecraft bus for VERITAS will be manufactured by Lockheed Martin.

The mission’s radar will be developed by JPL in partnership with ASI, the Italian space agency. Italy will also provide the mission’s high-gain antenna.

DLR, the German space agency, is providing the infrared spectrometer for the VERITAS mission, and will assist in radar data processing. The French space agency, CNES, will provide components for the spacecraft’s Ka-band communications system, Smrekar said.

VERITAS will also carry a deep space atomic clock built by JPL as a technology experiment. The atomic clock will help enable autonomous spacecraft maneuvers and enhance radio science observations to study the interior of Venus, NASA said.

Smrekar said the VERITAS mission will take about four months to travel from Earth and enter orbit around Venus.

DAVINCI+ and VERITAS join the successful “Discovery” line of NASA interplanetary missions.

Previous Discovery-class missions included the Dawn spacecraft, which orbited two of the largest objects in the asteroid belt, the Messenger mission to Mercury, and the InSight lander currently listening for seismic activity on Mars. Two Discovery missions selected in 2017 — named Lucy and Psyche — are scheduled for launch in 2021 and 2022 to begin missions focused on asteroid exploration.

“It is astounding how little we know about Venus, but the combined results of these missions will tell us about the planet from the clouds in its sky through the volcanoes on its surface all the way down to its very core,” said Tom Wagner, NASA’s Discovery program scientist. “It will be as if we have rediscovered the planet.”

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Follow Stephen Clark on Twitter: @StephenClark1.


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