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The Vega Mission and its Impacts on our Understanding of Venus and Halley’s Comet

Sushihorse

ESS 102: Space and Space Travel

March 11th, 2025

Abstract

In 1986, the Soviet Union while working with the French Space Agency launched Vega 1 and 2, aiming to learn about the composition of the Surface of Venus, learn about Venus’ atmosphere, and gather photos and information on Halley’s comet. Previous missions had gathered that Venus has no magnetic field, and that Venus’ atmosphere had strong winds. This mission found that the Atmosphere on Venus is thick with high winds, and that it’s much cooler than the surface temperature as well as information from Halley's comet. Lastly, the program failed to sample the surface due to the drill breaking on the lander. I am proposing Expedition, a Venus probe to learn more about the surface composition and pressures experienced on Venus. Knowing the similarities between Venus and Earth will help for understanding more of the possible effects of climate change, and will increase our knowledge of terrestrial planets.

Introduction

Venus has been observed since ancient times and can often be seen early in the morning or in the evening. It is the second planet from the Sun and the closest to Earth with a launch window every 19 months. It was also the target of the first interplanetary travel, with the first successful mission being Mariner 2 in 1962. The first several flyby missions before mariner 2 failed including Mariner 1 and Venera 1. The Soviet’s Venera program was focused entirely on Venus and the American Mariner program was focused on Venus, Mars and Mercury. The Mariner program found that Venus has an extremely hot surface and cool outer clouds. The data gained from Mariner 5 was analyzed with the data from Venera 4 which landed on the surface and survived briefly; this was a rare collaboration between America and the Soviet Union and happened in 1969. The Venera program got the first black and white photos of Venus, the first color photos, along with the first soft landing on a planet's surface. The Venera Program ended in 1983 with Venera 15 and 16 after they scanned around a quarter of the northern hemisphere of Venus.

Where the Venera Program ended, Vega began.

Both Vega probes were identical and were designed to provide information on the Venus atmosphere. While previous missions had determined it was thick with a permanent layer of clouds, there were many theories on how the sun and the volcanoes seen on Venus could affect the atmosphere. The Vega probes had balloons set up to track the speed of winds on both the night and day sides of Venus, along with the direction of travel.

Late in the program, when it was clear when the launch would happen, a second plan was added to the mission. A flyby of Halley’s Comet. The probes were equipped with extra Cameras to take photos of the asteroid along with the tail. It was also designed to measure the nucleus of Halley’s Comet.

Description

Both Vega spacecraft were identical and had a balloon and a lander module in addition to an outer probe that would go past Halley’s Comet, because both spacecraft were identical, I will not be saying both spacecraft again in this section.

Cameras:

The spacecraft had two cameras. One that was in color and one that was in black and white. These were used to take photos of Halley’s Comet. They were able to take wide angle and short angle photographs to capture the comet’s tail and the comet’s body itself.

The Cameras were built by both the Soviets and the French.

Spectrometers:

There were 5 different spectrometers on the spacecraft.

A Dust Mass Spectrometer, built by the Soviet Union, which measured the chemical contents and mass of the dust in the tail of Halley’s Comet.

A Neutral Gas Mass Spectrometer, built by the Soviet Union, to find the chemical composition of the Venus atmosphere.

An Ion Mass Spectrometer, built by the Soviet Union, used on the lander to find the composition of Venus’s surface.

An Infrared Spectrometer, built by France. It had three separate optical channels, two of which could record heat and the last could record images.

A three channel spectrometer, built by the Soviet Union, that could detect Ultraviolet, Visible, and Infrared light.

Other Instruments:

Two dust particle counters built by the Soviet Union. One detected Plasma, and the other was Acoustic and detected the amount of particles that it was hit by.

A Magnetometer to detect both a Venus magnetic field and if there was one on Halley’s Comet.

Observations and Results

The Vega project overall tested the Atmosphere of Venus and traced its wind patterns. It also got pictures from the surface of Venus and many of Halley’s Comet. The project also tested Halley’s Comet tail and determined that it had a nonspherical nucleus. The data gathered during the mission utilized both the NASA and Soviet antennas, which was a sign of how the cold war wasn’t always at high tensions.

Atmosphere:

The balloons on Vega 1 and 2 were released into the middle part of the atmosphere where the most activity occurs. Both balloons tracked their location including longitude, latitude, and height. Both balloons experienced strong winds and sent back data every time their speed changed by more than 1 m/s. Balloon 1 averaged around 69 m/s and Balloon 2 averaged around 66 m/s.

Both balloons experienced larger speed changes once passing into the day side of Venus. This suggests that Solar Wind plays an important role in the atmosphere of Venus. The incredibly large changes in the data of Balloon 2 however is not completely understood. The balloon may have experienced incredibly fast speeds due to being directly over a known mountain range, or it may have temporarily had problems with its oscillator.

Landers:

Of the landers on each Vega spacecraft, only the lander on Vega 2 provided data from the surface. The lander on Vega 1 was struck with strong winds and deployed its instruments before landing, and broke on contact with the surface.

The Vega 2 lander lasted for 56 minutes on the surface, and it landed almost exactly on the planetary radius with an altitude of 0.1km. The pressure at that point was 91atm and 736K. The surface sample taken was found to be an igneous rock commonly found on the Moon, and incredibly rare on Earth. This suggests the surface of Venus to be incredibly old. This may mean the surface of Venus hasn’t changed in this area since the planet’s last impact or that the main driving force of surface change is Volcanoes.

Halley’s Comet:

Both Vega 1 and 2 moved past Halley’s Comet before any other probe did. Vega 1 got within 14 million kilometers and Vega 2 got even closer a few days later with its closest being 8 thousand kilometers.

Both Spacecraft took images of Halley’s Comet. Vega 1 got the first images of the nucleus of Halley’s Comet. The images taken by Vega 2 were clearer due to both its closer proximity and there being less dust in the tail during its imaging. These images were able to help determine the size and shape of the comet nucleus being roughly 15.3 km x 7.2 km x 7.2 km. These results were similar to Giotto, an ESA probe that saw Halley’s Comet shortly after the Vega probes. Halley’s Comet has been described to be shaped like a Peanut, an Avocado, or a Potato, with many images showing an incredibly varied surface across its angles.

Vega 1 observed Halley’s Comet to have a surface temperature ranging from 300-400 K. This large difference combined with other probes data may mean that Halley’s Comet, and that comets in general only have the surface facing the solar wind go through sublimation, while the rest stays insulated by the tail.

Future Mission

Since the Vega Program, more information has been discovered about Venus. The Magellan Spacecraft launched by NASA in the 90s created a 3d map of the entire surface of Venus. This found that most of the surface is incredibly young, with few craters. This changed our understanding from Vega of the surface potentially being old. In addition, most of the surface is shaped by volcanoes, with lava pools, lava rivers, and volcanic ranges covering much of the surface.

Since Magellan, the only other probe dedicated to Venus was the Venus Express by ESA. This probe studied the Atmosphere of Venus and found that winds typically very between 60-70km/s. This matches up with the balloon data. In addition, Magellan took a color image of Venus revealing the atmosphere clouds as boring and white.

All current proposed missions to Venus are to continue study on the atmosphere. This is absurd. I am proposing a probe named Expedition, to aid in our continued understanding of terrestrial planets. None of the data we currently have on the surface has been updated since the Vega Mission back in 1986. The technological advancements since 1986 are immense.

Why:

This mission should happen because we currently do not have enough data points to say with certainty what is going on at the surface of Venus. While we know much about the surface of Mars, Earth, and the Moon, we still do know much about the surface of Venus, the other easily accessible terrestrial object. This increased knowledge of terrestrial planets will lead to increased understanding of what material was available in our solar system for our planets to form, and may translate to a greater understanding of planetary systems outside of our own.

Instruments:

Barometer. There has been very little data done on how the Pressure at the surface of Venus differs at different altitudes. In addition, this probe will be landing at a significantly different altitude, in the highlands of Lada Terra.

Spectroscopy for surface composition. We need more data points for the surface composition. While the surface is likely all igneous rocks, what type of igneous rocks. Will we find the surface to have more rock similar to the surface of the Moon, or rocks easily found on Earth?

Drill. Drilling several inches below the surface will be more likely to give us an untainted source for the Spectroscopy to analyze.

Spectroscopy for Atmospheric composition. There has not been updated information on how the Venusian atmosphere differs at different levels of the surface since 1986.

Probe Plan:

This Probe will be launched around 2036. It will land in the Highlands in the Lada Terra Quadangle, located on the southern side of Venus. The highlands in Lada Terra are characterized by large belts, suggesting they were formed by crust deformation. Drilling here will be beneficial as it will likely differ from previous samples as it is not directly from lava flows, giving greater insight into the surface composition of Venus.

When it gets to Venus, it will lithobrake and utilize the incredibly thick atmosphere to fall to the surface with no parachute. Once landed, the probe will drill into the surface, and test the composition of the rock. Lastly, it will test the pressure at the surface. It will likely melt within a few hours of landing on the surface.

How to Prevent Melting:

The Probe will be covered in a strong insulated shield to protect the instruments from the extreme temperatures caused by the lithobrake and act as a refrigerator on the surface, preventing the probe from getting too warm as it completes the mission.

Conclusion

The Vega program was an incredibly important mission for our understanding of Venus and Halley’s Comet. It provided information on the surface of Venus, as well as the atmosphere, surface temperatures, and the surface pressure. It also provided information about the nucleus of Halley’s Comet, including size and shape.

While important, these discoveries can still be improved upon, as we still know little about the planet outside of orbiters. It is time to make another trip down to the surface of Venus, and give it another go.

Annotated Citations

Abergel J., Bertaux G., Avanessov G.A., Tarnopolsky V.I., Zhulov B.S., Kondor A., Merenyi E., Foldy C., Szego K., Toth I., and A. V. Dyachkov, VEGA2 TV SYSTEM IMAGES PROCESSED BY KFKI V1.0, VEGA2-C-TVS-3-RDR-HALLEY-PROCESSED-V1.0, NASA Planetary Data System, 1997

All the processed images gathered by the Vega Mission. Useful for Observations and Results.

Preston; et al. (1986, March 21). "Determination of Venus Winds by Ground-Based Radio Tracking of the VEGA Balloons". Science. 231 (4744): 1414–1416. doi:10.1126/science.231.4744.1414.

All about the winds found on Venus from the balloons placed into the atmosphere with minimal data on where the balloons were at the time of speeds. This article goes into depth on the speed of the balloons in flight along the total time of flight. This will be useful for the description and results.

Gallentine, S.,(2021, April 20) The First Flight On Another World Wasn’t on Mars. It Was on Venus, 36 Years Ago. Smithsonian.https://www.smithsonianmag.com/air-space-magazine/ireali-first-flight-another-world-180977540/

Lots of good information on the balloons' descent and some more information the balloons got like temperature and height. This article also has lots of good information on how the balloon worked. This will be useful for both the description and the follow up mission.

Williams, David R.,(2022, October 28) Vega 1 NASA Space Science Data Coordinated Archive. https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1984-125A

This article tells a lot about the descent module that gathered information about the surface temperatures and composition. It also gives a lot of information on the instruments onboard and how the lander got the information it did. This will be useful for the results.

Pike, J (2019, April 8) Vega Veneras Comet Program GlobalSecurity.org https://www.globalsecurity.org/space/world/russia/vega-veneras.htm

This article contains a lot of the information on the instruments included on the Vega 1 and 2 probes including where they were built. It also includes a lot of information on the results from the flyby of Halley’s comet such as the pictures taken and what damage the probes went through while close to the comet. This will be useful for the observations and results.

Kumar, P.J., and Head, J.W. (2014, April 30) Geologic Map of the Lada Terra Quadrangle (V-56), Venus United States Geological Survey https://pubs.usgs.gov/sim/3249/pdf/sim3249_pamphlet.pdf

This pamphlet linked to a map of the Lada Terra region mentions the important parts of this section of Venus. This will be useful for the Future Mission