Category Archives: ESA

Saturn at Opposition from Hubble

A beautiful image of Saturn and some of its moons from the Hubble Space Telescope.

Credit: NASA, ESA, A. Simon (GSFC) and the OPAL Team, and J. DePasquale (STScI); CC BY 4.0

Original caption: \Cassini ended its 13-year mission at Saturn on 15 September 2017 when it plunged into the gas giant’s atmosphere, but the NASA/ESA Hubble Space Telescope is still keeping an eye on the ringed planet.

This is a composite image taken by Hubble on 6 June 2018 showing a fully-illuminated Saturn and its rings, along with six of its 62 known moons. The visible moons are (from left to right) Dione, Enceladus, Tethys, Janus, Epimetheus and Mimas (click here for an annotated version). Dione is the largest moon in the picture, with a diameter of 1123 km, compared to the smallest, oddly-shaped Epimetheus with a diameter around 116 km.

During Cassini’s mission, Enceladus was identified as one of the most intriguing moons, with the discovery of water vapour jets spewing from the surface implying the existence of a subsurface ocean. Icy moons with subsurface oceans could potentially offer the conditions to harbour life, and understanding their origins and properties are essential for furthering our knowledge of the Solar System. ESA’s JUpiter ICy moons Explorer (Juice), due to launch in 2022, aims to continue this theme by studying Jupiter’s ocean-bearing moons: Ganymede, Europa, and Callisto.

The Hubble image shown here was taken shortly before Saturn’s opposition on 27 June, when the Sun, Earth and Saturn were aligned so that the Sun fully illuminated Saturn as seen from Earth. Saturn’s closest approach to Earth occurs around the same time as opposition, which makes it appear brighter and larger and allows the planet to be imaged in greater detail.

In this image the planet’s rings are seen near their maximum tilt towards Earth. Towards the end of Cassini’s mission, the spacecraft made multiple dives through the gap between Saturn and its rings, gathering spectacular data in this previously unchartered territory.

The image also shows a hexagonal atmospheric feature around the north pole, with the remnants of a storm, seen as a string of bright clouds. The hexagon-shaped cloud phenomenon is a stable and persistent feature first seen by the Voyager 1 space probe when it flew past Saturn 1981. In a study published just last week, scientists using Cassini data collected between 2013 and 2017, as the planet approached northern summer, identified a hexagonal vortex above the cloud structure, showing there is still much to learn about the dynamics of Saturn’s atmosphere.

The Hubble observations making up this image were performed as part of the Outer Planet Atmospheres Legacy (OPAL) project, which uses Hubble to observe the outer planets to understand the dynamics and evolution of their complex atmospheres. This was the first time that Saturn was imaged as part of OPAL. This image was first published on 26 July.

Anticrepuscular Rays over Southern Tuscany

This glorious image from C) Ollie Taylor (limks below), via ESA illustrates wonderfully one of my favorite things – Atmospheric Optics.

Keep an eye on the sky and you too can see many of the optical effects described in my favorite atmospheric optics site, oddly enough named Atmospheric Optics – check it out and see what you can put to use, I think it’s great fun when it works out. The coolest thing I think I’ve seen and I may have a picture of it is the supernumerary rainbow.

Here is ESA’s caption to this great photo: This panorama comprises five images showing the Sun setting over the medieval and Renaissance town of Montepulciano, southern Tuscany.

While the enormous ball of hot gas that is our star cannot be directly seen, its presence is suggested by the radiant streams of light emanating from below the horizon — called anticrepuscular rays, or antisolar rays.

Despite appearing to meet at a point just below the horizon, the rays are in fact near-parallel beams of sunlight. Similar to the way that parallel railway lines seem to converge at a point in the distance, this is a trick of perspective; while these rays of sunlight do eventually meet at the Sun, it is a great deal further away than they make it appear.

Earth’s atmosphere, made up of gases, particulates and clouds, has shaped the way humans have seen the Sun for as long as they have been able to perceive it, for example making the white-hot star appear yellow against a blue sky, masking the infinite blackness of space.

However, as soon as we get past this protective layer, the true effect of our raging Sun becomes apparent in the fast changing, and potentially harmful environment of space, where space weather rules.

Space weather refers to the environmental conditions in space as influenced by solar activity; besides emitting a continuous stream of electrically charged atomic particles, the Sun periodically emits billions of tonnes of material threaded with magnetic fields in colossal-scale ‘coronal mass ejections’.

These ‘solar sneezes’ can and have caused significant disruption to Earth’s protective magnetic bubble and upper atmosphere, affecting satellites in orbit, navigation systems, terrestrial power grids, and data and communication networks. A recent ESA study estimated the potential impact in Europe from a single, extreme space weather event could be about €15 billion.

For this reason, ESA is planning a new mission to monitor the Sun’s activity and provide early warnings. The spacecraft will be positioned between the Sun and Earth at a special position called the fifth Lagrange point. From here, it can observe the ‘side’ of our star, detecting rapidly changing solar activity before it reaches Earth, providing much-needed warning of extreme weather events, allowing measures to be taken to protect and minimise any possible damage to satellites in orbit or infrastructure on Earth.

More images by UK-based photographer Ollie Taylor can be found on his website, or via Instagram and Facebook.

Remember SMART-1?

2006? My memory is pretty good; I remember this mission vividly including the flash at impact. Just not what year, they all kind of blend together sometimes (LOL).

Anyway, thanks ESA for this remembrance.

ESA: This greyscale, mottled image shows a patch of the Moon’s surface, and features an intriguing shape towards the top of the frame. This was actually made by a spacecraft – it marks the final resting place of ESA’s SMART-1 (Small Missions for Advanced Research in Technology-1).

Launched in 2003, SMART-1 was a Moon-orbiting probe that observed our cosmic companion for roughly three years. On 3 September 2006 the mission’s operations came to an end and the spacecraft was sent down to deliberately crash into the Moon, bouncing and grazing across the lunar surface at a speed of two kilometres per second and achieving Europe’s first lunar touchdown.

After the impact, a bright flash was seen at the boundary between lunar day and night by the Canada-France-Hawaii Telescope in Hawaii. However, as no other spacecraft were currently in orbit at the time to watch the event unfurl, it was not possible to pinpoint exactly where SMART-1 crashed. Scientists used orbit tracking, Earth-based simulations, and observations of the bright impact flash to estimate the location of the landing site, but the mission’s precise resting place remained unknown for over a decade.

Last year, high-resolution images from NASA’s Lunar Reconnaissance Orbiter (LRO) revealed the whereabouts of SMART-1 – as shown here. The spacecraft carved out a four-metre-wide and 20-metre-long gouge as it it impacted and bounced at 34.262° south, 46.193° west. It cut across a small crater and sent lunar soil flying outwards from its skidding, ricocheting path, creating the brighter patches of material seen either side of the crater, with debris from spacecraft and oblique dust ejecta coming to a halt several to tens of kilometres in the forward stream direction.

Alongside searching for water ice on the Moon and observing and photographing our nearest celestial neighbour, SMART-1 played a key role in testing ion propulsion – an efficient type of propulsion that uses electrical energy to propel a spacecraft through space.

SMART-1 was ESA’s first mission to travel to deep space using this type of propulsion. Ion propulsion will also be used on the joint ESA-JAXA BepiColombo mission when it launches in October of this year towards Mercury.

The field of view in the image is 50 metres wide (north is up), with solar illumination coming from the west. SMART-1 touched down from north to south.

More about SMART-1

Copyright P. Stooke/B. Foing et al 2017/ NASA/GSFC/Arizona State University

Wind and Water

First the wind, this is how ESA’s Aeolus satellite will use laser technology to measure the winds to help understand our climate and to improve our weather forecasts.

Next the water, an ESA-backed group, led by TCarta, has developed a way of using data from Low-orbiting satellites equipped with light-measuring sensors to produce water depth maps AND make them available to anyone who could use them.

Both videos copyright by ESA.

Gaia’s Star Density Map

A star density map composed by data obtained from second data release of Gaia – not to mention a very resourceful individual.

ESA: The second data release of ESA’s Gaia mission, made in April, has marked a turning point in the study of our Galactic home, the Milky Way. With an unprecedented catalogue of 3D positions and 2D motions of more than a billion stars, plus additional information on smaller subsets of stars and other celestial sources, Gaia has provided astronomers with an astonishing resource to explore the distribution and composition of the Galaxy and to investigate its past and future evolution.

The majority of stars in the Milky Way are located in the Galactic disc, which has a flattened shape characterised by a pattern of spiral arms similar to that observed in spiral galaxies beyond our own. However, it is particularly challenging to reconstruct the distribution of stars in the disc, and especially the design of the Milky Way’s arms, because of our position within the disc itself.

This is where Gaia’s measurements can make the difference.

This image shows a 3D map obtained by focusing on one particular type of object: OB stars, the hottest, brightest and most massive stars in our Galaxy. Because these stars have relatively short lives – up to a few tens of million years – they are mostly found close to their formation sites in the Galactic disc. As such, they can be used to trace the overall distribution of young stars, star formation sites, and the Galaxy’s spiral arms.

The map, based on 400,000 of this type of star within less than 10 000 light-years from the Sun, was created by Kevin Jardine, a software developer and amateur astronomer with an interest in mapping the Milky Way using a variety of astronomical data.

It is centred on the Sun and shows the Galactic disc as if we were looking at it face-on from a vantage point outside the Galaxy.

To deal with the massive number of stars in the Gaia catalogue, Kevin made use of so-called density isosurfaces, a technique that is routinely used in many practical applications, for example to visualise the tissue of organs of bones in CT scans of the human body. In this technique, the 3D distribution of individual points is represented in terms of one or more smooth surfaces that delimit regions with a different density of points.

Here, regions of the Galactic disc are shown with different colours depending on the density of ionising stars recorded by Gaia; these are the hottest among OB stars, shining with ultraviolet radiation that knocks electrons off hydrogen atoms to give them their ionized state.

The regions with the highest density of these stars are displayed in pink/purple shades, regions with intermediate density in violet/light blue, and low-density regions in dark blue. Additional information from other astronomical surveys was also used to map concentrations of interstellar dust, shown in green, while known clouds of ionised gas are depicted as red spheres.

The appearance of ‘spokes’ is a combination of dust clouds blocking the view to stars behind them and a stretching effect of the distribution of stars along the line of sight.

An interactive version of this map is also available as part of Gaia Sky, a real-time, 3D astronomy visualisation software that was developed in the framework of the Gaia mission at the Astronomisches Rechen-Institut, University of Heidelberg, Germany.

Further details including annotated version of the map: Mapping and visualising Gaia DR2

Credits: Galaxy Map / K. Jardine

Proba’s Solar Eclipses

ESA: Thanks to a quirk of our cosmos, the Moon’s average distance from Earth is just right for it to appear as the same size in the sky as the significantly larger Sun. Once in a while the Moon slides directly between Earth and the Sun such that it appears to cover our star completely, temporarily blocking out its light and creating a total solar eclipse for those along the narrow path cast by the Moon’s shadow.

But sometimes the alignment is such that the Moon only partially covers the Sun’s disc. Such a partial eclipse occurred on Saturday for observers located primarily in northern and eastern Europe, northern parts of North America, and some northern locations in Asia.

ESA’s Sun-watching Proba-2 satellite orbits Earth about 14.5 times per day and with its constant change in viewing angle, it dipped in and out of the Moon’s shadow twice during Saturday’s eclipse.

Selected views of the two partial eclipses are seen side-by-side here – the first (left) was captured at 08:40:12 GMT and the second (right) at 10:32:17 GMT on 11 August.

The images were taken by the satellite’s SWAP camera, which works at extreme ultraviolet wavelengths to capture the Sun’s hot turbulent atmosphere – the corona – at temperatures of about a million degrees, which can be seen in the background.

Watch the full image sequence here.

Image: ESA/Royal Observatory of Belgium

A Bit of Asteroid Itokawa

Along with the likes of the Cassini and Rosetta missions we have the history making Hayabusa Mission. The mission actually returned a sample from the asteroid Itokawa and the mission at least for me showcases the resilience of the JAXA mission team (see the section “Changes in mission plan” in the provided link.

The image above was released yesterday 01 Aug 2018 by ESA.

Here’s the caption included in the release:

ESA: Seen on a microscopic support, this sharp-edged grain of rock is an extraterrestrial object – a tiny sample from the Itokawa asteroid, retrieved by Japan’s Hayabusa mission and now being tested by ESA researchers.

Japan’s Hayabusa spacecraft was the world’s first mission to retrieve samples from the surface of an asteroid and return them to Earth. Beset by many problems, after a seven-year, six-billion-km odyssey Hayabusa returned around 1 500 precious asteroid grains to Earth.

Extremely precious, these Hayabusa grains have become the focus of scientific study around the world – and three of them are currently here, at ESA’s ESTEC technical centre in the Netherlands.

Researcher Fabrice Cipriani is leading research into their static charging properties, to understand the consequences for the surface environments of asteroids.

FENIX The Little Boosters That Can

I love this idea!

ESA: Sometimes the key to innovation is staying simple. Italian tech company D-Orbit applied this principle to their winning product submitted to last year’s Space Exploration Masters.

The competition encourages ideas to solve some of the space industry’s main challenges while fostering products and services with commercial potential.

In the case of D-Orbit’s Fenix propulsion system, the idea was both simple and small. The pen-sized booster prototype, is just 10 cm long and 2 cm wide – allowing small satellites to work smarter and explore farther.

The 10 x 10 x 10 cm CubeSats are deployed directly into orbit from space. They currently have no propulsion system to change orbit or deorbit at the end of their missions. With the FENIX, CubeSats could be employed for longer missions farther out in space.

Each of the four boosters is packed with solid propellant that provides thrust which is triggered by a simple electrical ignition system. The boosters can be configured at each corner of the CubeSat or doubled up on either side. Thanks to their lightweight and compact size, they do not take up much instrument space.

With space exploration opening for business, technologies like Fenix have the potential to expand our horizons farther out in space. CubeSats can take on more sophisticated missions if they can manoeuvre in orbits – such as studying the Moon and asteroids from different angles.

In low Earth orbit, the boosters can deorbit the CubeSats at the end of their missions to help reduce space debris.

D-Orbit won a four-month ticket to test their prototype on the newly-installed ICE Cubes facility in the Columbus module of the International Space Station. The team will test the booster’s safe ignition mechanism inside an ICE cube experiment unit, without firing the actual propulsion system, to ensure that it works and is safe under space conditions.

Sensors and cameras will record the sparks, triggered by an electrical impulse, and the team can observe the testing anytime, anywhere, thanks to ICE Cubes dedicated control centre providing continuous remote access for users on ground. Fenix is set for launch to the Space Station by the end of next year.

Do you have an idea with commercial potential that could innovate space exploration? Submit it to the Space Exploration Masters challenge.

Image: ESA