OrbitalHub

ESA dixit:

“ESA’s Swarm satellites are seeing fine details in one of the most difficult layers of Earth’s magnetic field to unpick – as well as our planet’s magnetic history imprinted on Earth’s crust. Earth’s magnetic field can be thought of as a huge cocoon, protecting us from cosmic radiation and charged particles that bombard our planet in solar wind. Without it, life as we know it would not exist. Most of the field is generated at depths greater than 3000 km by the movement of molten iron in the outer core. The remaining 6% is partly due to electrical currents in space surrounding Earth, and partly due to magnetised rocks in the upper lithosphere – the rigid outer part of Earth, consisting of the crust and upper mantle.

Although this ‘lithospheric magnetic field’ is very weak and therefore difficult to detect from space, the Swarm trio is able to map its magnetic signals. After three years of collecting data, the highest resolution map of this field from space to date has been released.

“By combining Swarm measurements with historical data from the German CHAMP satellite, and using a new modelling technique, it was possible to extract the tiny magnetic signals of crustal magnetisation,” explained Nils Olsen from the Technical University of Denmark, one of the scientists behind the new map. ESA’s Swarm mission manager, Rune Floberghagen, added: “Understanding the crust of our home planet is no easy feat. We can’t simply drill through it to measure its structure, composition and history. “Measurements from space have great value as they offer a sharp global view on the magnetic structure of our planet’s rigid outer shell.”

The magnetic field is in a permanent state of flux. Magnetic north wanders, and every few hundred thousand years the polarity flips so that a compass would point south instead of north. When new crust is generated through volcanic activity, mainly along the ocean floor, iron-rich minerals in the solidifying magma are oriented towards magnetic north, thus capturing a ‘snapshot’ of the magnetic field in the state it was in when the rocks cooled. Since magnetic poles flip back and forth over time, the solidified minerals form ‘stripes’ on the seafloor and provide a record of Earth’s magnetic history.”

Video credit: ESA

ESA dixit:

“Space debris – a journey to Earth takes the audience on a journey from the outer solar system back to our home planet. The objects encountered along the way are man made. Originally designed to explore the universe, these are now a challenge for modern space flight. An estimated number of 700,000 objects larger than 1 cm and 170 million objects larger than 1 mm are expected to reside in Earth orbits.

The video gives a closer look at the different regions used for space flight and explains how mitigation and removal measures could preserve future usage of these orbits.”

Video credit: ESA/ID&Sense/ONiRiXEL, CC BY-SA 3.0 IGO

ESA dixit:

“The ExoMars Rover, developed by ESA, provides key mission capabilities: surface mobility, subsurface drilling and automatic sample collection, processing, and distribution to instruments. It hosts a suite of analytical instruments dedicated to exobiology and geochemistry research: this is the Pasteur payload.

The Rover uses solar panels to generate the required electrical power, and is designed to survive the cold Martian nights with the help of novel batteries and heater units. Due to the infrequent communication opportunities, only 1 or 2 short sessions per sol (Martian day), the ExoMars Rover is highly autonomous. Scientists on Earth will designate target destinations on the basis of compressed stereo images acquired by the cameras mounted on the Rover mast.

The Rover must then calculate navigation solutions and safely travel approximately 100 m per sol. To achieve this, it creates digital maps from navigation stereo cameras and computes a suitable trajectory. Close-up collision avoidance cameras are used to ensure safety.

The locomotion is achieved through six wheels. Each wheel pair is suspended on an independently pivoted bogie (the articulated assembly holding the wheel drives), and each wheel can be independently steered and driven. All wheels can be individually pivoted to adjust the Rover height and angle with respect to the local surface, and to create a sort of walking ability, particularly useful in soft, non-cohesive soils like dunes. In addition, inclinometers and gyroscopes are used to enhance the motion control robustness. Finally, Sun sensors are utilised to determine the Rover’s absolute attitude on the Martian surface and the direction to Earth.

The camera system’s images, combined with ground penetrating radar data collected while travelling, will allow scientists on-ground to define suitable drilling locations.The Rover subsurface sampling device will then autonomously drill to the required depth (maximum 2 m) while investigating the borehole wall mineralogy, and collect a small sample. This sample will be delivered to the analytical laboratory in the heart of the vehicle. The laboratory hosts four different instruments and several support mechanisms. The sample will be crushed into a fine powder. By means of a dosing station the powder will then be presented to other instruments for performing a detailed chemistry, physical, and spectral analyses.”

Video credit: ESA

ESA dixit:

“The motion of two million stars is traced 5 million years into the future using data from the Tycho-Gaia Astrometric Solution, one of the products of the first Gaia data release. This provides a preview of the stellar motions that will be revealed in Gaia’s future data releases, which will enable scientists to investigate the formation history of our Galaxy.

Stars move through our Galaxy, the Milky Way, although the changes in their positions on the sky are too small and slow to be appreciated with the naked eye over human timescales. These changes were first discovered in the eighteenth century by Edmond Halley, who compared stellar catalogues from his time to a catalogue compiled by the astronomer Hipparchus some two thousand years before. Nowadays, stellar motions can be detected with a few years’ worth of high-precision astrometric observations, and ESA’s Gaia satellite is currently leading the effort to pin them down at unprecedented accuracy.

A star’s velocity through space is described by the proper motion, which can be measured by monitoring the movement of a star across the sky, and the radial velocity, which quantifies the star’s motion towards or away from us. The latter can be inferred from the shift towards blue or red wavelengths of certain features – absorption lines – in the star’s spectrum.

Launched in 2013, Gaia started scientific operations in July 2014, scanning the sky repeatedly to obtain the most detailed 3D map of our Galaxy ever made. The first data release, published in September 2016, was based on data collected during Gaia’s first 14 months of observations and comprised a list of 2D positions – on the plane of the sky – for more than one billion stars, as well as distances and proper motions for a subset of more than two million stars in the combined Tycho–Gaia Astrometric Solution, or TGAS.
The TGAS dataset consists of stars in common between Gaia’s first year and the earlier Hipparcos and Tycho-2 Catalogues, both derived from ESA’s Hipparcos mission, which charted the sky more than two decades ago.

This video shows the 2 057 050 stars from the TGAS sample, with the addition of 24 320 bright stars from the Hipparcos Catalogue that are not included in Gaia’s first data release. The stars are plotted in Galactic coordinates and using a rectangular projection: in this, the plane of the Milky Way stands out as the horizontal band with greater density of stars. Brighter stars are shown as larger circles, and an indication of the true colour of each star is also provided; information about brightness and colour is based on the Tycho-2 catalogue from the Hipparcos mission.

The video starts from the positions of stars as measured by Gaia between 2014 and 2015, and shows how these positions are expected to evolve in the future, based on the proper motions from TGAS. The frames in the video are separated by 750 years, and the overall sequence covers 5 million years. The stripes visible in the early frames reflect the way Gaia scans the sky and the preliminary nature of the first data release; these artefacts are gradually washed out in the video as stars move across the sky.”

Video credit: ESA

ESA dixit:

“The JUpiter ICy moons Explorer (JUICE) is the first L-class mission within ESA’s Cosmic Vision programme. It aims at a comprehensive exploration of the Jovian system with particular emphasis on Jupiter, its environment, and Galilean moons Ganymede, Europa and Callisto by investigating them as planetary bodies and potential habitats.

Scheduled for launch in 2022, with arrival in the Jovian system in 2029, JUICE will spend three-and-a-half years examining the giant planet’s turbulent atmosphere, enormous magnetosphere, its set of tenuous dark rings and its satellites. It will study the large icy moons Ganymede, Europa and Callisto, which are thought to have oceans of liquid water beneath their icy crusts – perhaps even harbouring habitable environments. The mission will culminate in a dedicated, eight-month tour around Ganymede, the first time any moon beyond our own has been orbited by a spacecraft.

JUICE will be equipped with 10 state-of-the-art instruments, including cameras, an ice-penetrating radar, an altimeter, radio-science experiments, and sensors to monitor the magnetic fields and charged particles in the Jovian system. In order to ensure it can address these goals in the challenging Jovian environment, the spacecraft’s design has to meet stringent requirements. An important milestone was reached earlier this month, when the preliminary design of JUICE and its interfaces with the scientific instruments and the ground stations were fixed, which will now allow a prototype spacecraft to be built for rigorous testing. The review also confirmed that the 5.3 tonne spacecraft will be compatible with its Ariane 5 launcher.

Operating in the outer Solar System, far from the Sun, means that JUICE needs a large solar array: two wings of five panels each are foreseen, which will cover a total surface area of nearly 100 m², capable of providing 820 W at Jupiter by the end of the mission. After launch, JUICE will make five gravity-assist flybys in total: one each at Mars and Venus, and three at Earth, to set it on course for Jupiter. Its solar panels will have to cope with a range of temperatures such that when it is flying closer to the Sun during the Venus flyby, the solar wings will be tilted to avoid excessive temperatures damaging the solar cells.

The spacecraft’s main engine will be used to enter orbit around the giant planet, and later around Jupiter’s largest moon, Ganymede. As such, the engine design has also been critically reviewed at this stage. Special measures will allow JUICE to cope with the extremely harsh radiation that it must endure for several years around Jupiter. This means careful selection of components and materials, as well as radiation shielding. One particularly important topic is JUICE’s electromagnetic ‘cleanliness’. Because a key goal is to monitor the magnetic fields and charged particles at Jupiter, it is imperative that any electromagnetic fields generated by the spacecraft itself do not interfere with the sensitive scientific measurements. This will be achieved by the careful design of the solar array electrical architecture, the power distribution unit, and the reaction wheels – a type of flywheel that stabilizes the attitude.

[…]JUICE will meet strict planetary protection guidelines, because it is imperative to minimize the risk that the potentially habitable ocean moons, particularly Europa, might be contaminated by viruses, bacteria or spores carried by the spacecraft from Earth. Therefore, mission plans ensure that JUICE will not crash into Europa, on a timescale of hundreds of years.”

Video credit: ESA

NASA dixit:

“On January 14, 2005, ESA’s Huygens probe made its descent to the surface of Saturn’s hazy moon, Titan. Carried to Saturn by NASA’s Cassini spacecraft, Huygens made the most distant landing ever on another world, and the only landing on a body in the outer solar system. This video uses actual images taken by the probe during its two-and-a-half hour fall under its parachutes.

Huygens was a signature achievement of the international Cassini-Huygens mission, which will conclude on September 15, 2017, when Cassini plunges into Saturn’s atmosphere.”

Video credit: NASA Jet Propulsion Laboratory