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STARDUST mission

Collected and translated from the NASA website, by Aryeh Morg, courtesy of the Israel Astronomical Society

background

STARDUST, is the first American space mission dedicated solely to the study of a comet, and the first robotic mission planned to return material from outer space, beyond the lunar orbit.

The STARDUST spacecraft was launched on February 7, 1999, from Cape Canaveral, Florida on a Delta II rocket.

STARDUST's basic purpose was to collect dust and carbon-based samples, during the closest encounter with comet WILD 2 - known as "VILT 2" after its Swiss discoverer. The meeting was planned and carried out in January 2004, after almost 4 years of space flight.

The STARDUST space capsule brought with it samples of interstellar dust, including recently discovered dust that flows into the middle of our solar system from the Sagittarius group. These materials are assumed to contain primordial seeds/nuclei from the interstellar medium and nebulae, which include remnants from the formation of the solar system. Analysis of these amazing celestial particles is expected to yield important distinctions of the evolution of the Sun and its planets and even the origin of life. An additional payload was placed on the spacecraft, including a mass spectrometer, a monitor for measuring dust flow, a CCD camera for optical navigation, and a radio transmitter-receiver. These additional devices will complete and verify data, to those that will be produced from the particles that will be collected.

As for the Willd 2 comet, the main goal was to collect particles with a diameter greater than 15 microns, with the help of the Airgel recorder (see also below). As for the interstellar dust particles, the intention was to expose the spacecraft to the dust stream for at least 150 days. These particles were trapped in the variable density medium of the shaped airgel, without damage, in order to preserve at least the elements, the chemical and isotopic compounds, and the morphological forms of the submicron particles.

Scientific review on Stardust

When you think of a comet, it is natural to think of Halley's Comet because it is so well known and easy to observe, while it passes near the Earth. There are many other comets, some new "guests" in our area of the solar system. One of them is the comet Wild 2, which did not pass near KDA until 1974, when the gravity of "Zedek" changed its trajectory. Now it moves closer to the Sun, between Jupiter and the Earth. Since it has not been exposed to the sun in the near term, its composition has not changed much since its formation. By the time Stardust met him, Wild 2 had made only five orbits around the sun. On the other hand, Halley's Comet circled the Sun more than a hundred times coming very close to the Sun, so its initial composition changed.

Five times a charm

When a comet gets close enough to the sun and heats up, it loses some of its material in a process of sublimation. This happens when a solid turns into a gas without first turning into a liquid. After 1,000 revolutions around the Sun, a comet loses most of its volatile components and no longer produces a cloud, consisting of gases that have evaporated from its surface. Since the volatile gases are the ones that transport the dust particles from the nucleus - the solid part of the comet, the comet no longer produces the beautiful dust tail that we are sometimes able to see in the sky at night.

Since Wild 2 has only passed the Sun a few times, it still has the dust and gases, and is still in its primordial state. It is important to note that comets are composed of materials left over from the Sun's nebula after the formation of the planets. Unlike the planets, comets have not changed significantly since the formation of the solar system. Therefore, comets may be the key to understanding the early evolution of the solar system. Comet Wild 2 may therefore contain a lot of this primordial material, making it an ideal choice for research.

in the right place at the right time

An important point of view of the Comet Wild 2 journey is the fact that it is in the right place at the right time, to visit. The Stardust mission was especially helped by the fact that the scientists were able to map the spacecraft's flight path to encounter the comet, in a time interval of relatively low speed. Due to this low encounter speed, the spacecraft was able to capture the cometary dust instead of it passing quickly through the dust collector.

Exploring the mysteries of comets

As a rule, comets consist of dust and icy gases. They move in highly elliptical orbits, which bring them close to the Sun, and then spin them back, deep into space. As usual, the furthest point they reach is beyond Pluto's orbit. Near the heat of the Sun, comets develop tails millions of kilometers long, and some create a spectacular sight when they pass near the Earth.

It seems that comets have appeared for centuries in an unexpected way, creating exaggerated reactions from the people who did not understand the phenomenon. They were blamed for everything from the death of kings, the destruction of empires and the emergence of epidemics. The passage of Halley's Comet in 1066, for example, allegedly predicted the defeat of the English at the Battle of Hasting. Recently, during its transit in 1910, during the development of spectroscopy, toxic gases were discovered in it. Taking advantage of the fear that the Earth will pass through the toxic tail, crooks sold insurance policies and homeopathic medicines to innocent people, against "comet fever".

In order to investigate the mysteries of comets, NASA's Stardust spacecraft passed near a comet, and for the first time ever, brought material back to Earth for research by scientists from around the world. Materials from this comet, it is hoped, will help solve some of the most hidden mysteries of these small bodies, sometimes described as "dirty ice balls" traveling through space. By studying, to one degree or another, these particles of a comet, scientists hope to discover something about the materials that created the universe, and possibly even about the origin of the universe. Another big question that scientists are looking for a better answer to is whether the comets brought water to Earth.

Capture comet dust with Aerogel

The initial goal of the Stardust mission was to capture both comet particles and interstellar dust. The main challenge to successfully achieve the goal involved slowing down the particles from their high speed, without increasing their temperature or other effects, which could cause physical changes. When the spacecraft met the comet, the collision speed of the particles was 6 times higher than the speed of a rifle bullet. Although each particle may be smaller than a grain of sand, high-velocity capture can change their shape and chemical composition, and even vaporize them completely.

In order to capture particles without causing them damage, Stardust used an exceptional material known as "aerogel". It is a silicon-based solid, with a porous sponge-like structure, in which 99.8 percent of the volume is empty space. For comparison, the density of airgel is 1,000 times lower than that of glass - an additional solid based on silicon. When a particle hits this material, it seemingly buries itself within the material, creating a path 200 times longer than its own length. This slows it down and brings the particle to a final stop, gradually. Thanks to the fact that the airgel is mostly transparent, with a shell of a special shade: smoky blue, the scientists will be able to use these paths to find the tiny particles.

The properties of the airgel

The airgel is not similar to ordinary foam, but a special porous material with microscopic pores, on a micron scale. It consists of individual components several nanometers in size, connected with high pore density. brokerage

This exception has unusual properties, such as low thermal conductivity, low refractive index and low sound speed - in addition to its unusual ability to capture dust moving at high speed. The airgel is produced at high temperature and pressure that reach a critical point, for the drying of a gel consisting of silicone molecules with solvent filling. Aerogel is created and approved as an aviation material at the Jet Propulsion Laboratory (JPL). This laboratory prepared an aerogel for the Pathfinder to Mars and the Stardust mission, which has controlled and pure properties. This special airgel approaches the density of air. It is strong and easily withstands launch and space environmental conditions. It has also been tested recently, on Space Shuttle and Space Laboratory II flights.

Oger "Tennis Racket"

The airgel in the Stardust spacecraft was installed inside a "hamster" shaped like a tennis racket. The hamster was designed to be protected in the reentry chamber from being exposed to space, during the flight. One side of the hamster will face the particles in Comet Wild 2, while the other side will face the stream of interstellar dust they will encounter during the flight.

When extremely high-velocity particles are trapped in the airgel, they create hollow conical paths that are easily seen in the high transparency of the material, using a stereo-microscope. This cone is wide at the point of entry, and the particle is held intact at the apex of the cone. This provides a method to determine which direction the dust grain came from, and is the basis for the approach of using a single sheet of airgel to capture both dust from the comet and the interstellar medium, from both directions without confusion.

After the encounter with comet Wild 2, the airgel storage will be placed in the sample chamber (SRC) and returned to Israel for detailed analysis by scientists at NASA's Johnson Space Center.

the flight plan

Planning a route while helping the Earth's gravitational acceleration allowed Stardust to capture dust from the comet at a relatively low speed of 6.1 km per second (for comparison, the Giotto spacecraft met Halley's comet at ten times the speed). With the help of the optical navigation system on the spacecraft, the levitation took place at a distance of about 300 kilometers from the comet's nucleus. This amazing route allowed for a launch, with low fuel consumption and using a medium version Delta II rocket.

Summary of the schedule

Launch - February 1999.

Assisting in the acceleration of gravity of KDWA - January 2001.

Encounter with the asteroid Annefrank - November 2002.

Meeting with the comet Wild 2 - January 2004.

Back to KDAHA - January 2006.

The Stardust spacecraft was launched on February 7, 1999. The first orbital loop lasted two years at a speed of 160 meters per second, on a Delta-V rocket and orbit corrections near the far center of the KDA orbit around the Sun

(Aphelion). The KDA pull "pumped" the spacecraft along a loop of 2.5 years, which the spacecraft performed twice. 198 days before the encounter and when the speed of the Delta-V rocket is 71 meters per second, the passage of the spacecraft near the comet was planned. This happened on January 2, 2004, at a distance of 1.86 AU and 98.5 days after the spacecraft's perihelion pass. An astronomical unit test was carried out during June-July 2003, in order to gauge the spacecraft's performance before returning to the Earth's sphere. The spacecraft approached the comet at a speed of 6.1 km per second, from the direction of the Sun at a phase angle of 73 degrees. The flight through the comet was on the side of the sun and at a distance of 300 km from it. The spacecraft passed by the comet 5 years from the launch date and the return to Earth will take another XNUMX years.

In total, three orbits around the sun were performed, in order to minimize the needs of the Delta V rocket to perform the mission so that a medium model of the rocket would fit. In addition, the three orbits allowed the most time for the collection of the interstellar dust.

the route

In order to rendezvous with Comet Wild 2, the spacecraft made three orbits around the Sun. On the second lap, her orbit crossed that of the comet. During the encounter, STARDUST performed a variety of tasks including reporting the amount of comet particles that hit the spacecraft during the encounter with the dust stream and measured on the monitor, and real-time analysis of these particle compounds and the volatile products collected by the comet and the dust probe. Using the airgel material, the spacecraft captured particles and stored them safely for the long journey back to Earth. In January 2006, Stardust and its precious cargo returned, by opening a parachute and entering the Earth's atmosphere with the 57 kg (125 lb) cell.

NASA's Discovery Program

Stardust is NASA's fourth mission following Pathfinder to Mars, encounters with near-Earth asteroids and the lunar exploration mission. Discovery Missions is an ongoing program that aims to offer the scientific community opportunities to obtain or complete high-quality common scientific research, using innovative and efficient management methods. The program aims for high performance at low cost by using cutting-edge technologies and maintaining strict cost limits.

Stardust is coming home

January 16, 2006: The Stardust research probe successfully landed on Sunday, January 15, 2006, at the highest penetration speed a spacecraft has ever entered the atmosphere. Its safe landing marked the end of a 7-year journey around the solar system.