Lee waves: Lee waves are a special type of cloud created by the wind encountering obstacles and build up on the ‘leeward‘ or downwind side. The geometries of the lee waves depend on the shape of the obstacles. Credit: ESA/DLR/FU Berlin.
Mars has always held a special place in our hearts, likely from hints over the decades of perhaps finding signs of life, albeit fossilised and primitive. It’s been the subject of study from telescopes and space missions alike, most notably ESA’s Mars Express which has been observing the red planet for 20 years. Over the two decades of observation it has studied an amazing variety of atmospheric phenomenon which have now been catalogued in a new ‘Cloud Atlas.’ Many will be familiar to sky watchers on Earth but some are very different.
This simulated perspective oblique view shows Olympus Mons, the tallest volcano not only on Mars but in the entire solar system. The volcano measures some 600 km across. CREDIT Credit: ESA/DLR/FU Berlin (A. Valantinas)
It’s been known for years that there are large quantities of water ice locked up in the Martian poles. Around the equator however it is a barren dry wasteland devoid of any surface ice. Recent observations of Mars have discovered frost on the giant shield volcanoes but it only appears briefly after sunrise and soon evaporates. Estimates suggest that 150,000 tons of water cycle between the surface and atmosphere on a daily basis.
Image of the Sun from Solar Orbiter (left Feb 2021 and right Oct 2023)
The solar cycle has been reasonably well understood since 1843 when Samuel Schwabe spent 17 years observing the variation of sunspots. Since then, we have regularly observed the ebb and flow of the sunspots cycle every 11 years. More recently ESA’s Solar Orbiter has taken regular images of the Sun to track the progress as we head towards the peak of the current solar cycle. Two recently released images from February 2021 and October 2023 show how things are really picking up as we head toward solar maximum.
The Horn of Africa and the Gulf of Aden are prominent in this Earth snapshot from the JMC1 camera on the European Space Agency's Juice probe, captured a half-hour after launch on April 14. Credit: ESA / Juice / JMC, CC BY-SA 3.0 IGO
The bus-sized probe is due to make four slingshot flybys of Earth and Venus to pick up some gravity-assisted boosts to its destination — and ESA mission managers plan to have the monitoring cameras running during those close encounters.
Direct images of AF Lep b, acquired by the SPHERE instrument on the VLT. Credit: ESO/Paranal Observatory
To date, astronomers have confirmed 5,272 exoplanets in 3,943 systems using a variety of detection methods. Of these, 1,834 are Neptune-like, 1,636 are gas giants (Jupiter-sized or larger), 1,602 are rocky planets several times the size and mass of Earth (Super-Earths), and 195 have been Earth-like. With so many exoplanets available for study (and next-generation instruments optimized for the task), the process is shifting from discovery to characterization. And discoveries, which are happening regularly, are providing teasers of what astronomers will likely see in the near future.
For example, two international teams of astronomers independently discovered a gas giant several times the mass of Jupiter orbiting a Sun-like star about 87.5 light-years from Earth. In a series of new papers that appeared in Astronomy & Astrophysics, the teams report the detection of a Super-Jupiter orbiting AF Leporis (AF Lep b) using a combination of astrometry and direct imaging. The images they acquired using the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) have since become the ESO’s Picture of the Week.
Comets, with their long, beautiful, bright tails of ice, are some of the most spectacular sightings in the night sky. This was most apparent when Comet NEOWISE passed by Earth in the summer of 2020, dazzling viewers from all over the planet while being mainly visible in the northern hemisphere. Even though the sky might look the same night after night, comets are a humble reminder that the universe is a very active and beautiful place.
An artists concept of the Solar Orbiter spacecraft studying the Sun. Credit: ESA.
The European Space Agency’s Solar Orbiter snaps an amazing image, en route to its first close pass near the Sun.
You’ve never seen the Sun like this. Earlier this month, the European Space Agency’s Solar Orbiter captured an amazing view of our host star.
The images were snapped on March 7th, as Solar Orbiter passed directly between the Earth and the Sun. There was an explicit reason for this, as the science team wanted to calibrate and compare the images with Earth-based and missions in Earth orbit, to include the Inouye solar observatory, NASA’s Solar Dynamics Observatory and the joint ESA/NASA Solar Heliospheric Observatory (SOHO), located at the Lagrange (L1) Sun-Earth point.
The sunshield of NASA’s James Webb Space Telescope sits deployed inside a cleanroom at Northrop Grumman Aerospace Systems in Redondo Beach, California, in October 2017. Credits: Northrop Grumman
At Europe’s Spaceport near Kourou in French Guiana, technicians are busy getting the James Webb Space Telescope (JWST) ready for launch. The observatory arrived at the facility on Oct. 12th and was placed inside the upper stage of the Ariane 5 rocket that will carry it to space on Nov. 11th. The upper stage was then hoisted high above the core stage and boosters so that a team of engineers could integrate them.
Unfortunately, an “incident” occurred shortly after when the engineers attempted to attach the upper stage to the launch vehicle adapter (LVA) to the launch vehicle. According to a NASA Blogs post, the incident involved the sudden release of a clamp band (which secures the JWST to the LVA), which sent vibrations throughout the observatory. According to NASA, this incident could push the JWST’s launch date (slated for Dec. 18th) to Dec. 22nd.
In November (or early December) of this year, after many excruciating delays, NASA’s James Webb Space Telescope (JWST) will finally launch to space. As the most advanced and complex observatory ever deployed, the James Webb will use its advanced suite of instruments to observe stars, exoplanets, and galaxies in the near and mid-infrared spectrum. In the process, it will address some of the most enduring mysteries about the nature of the Universe.
When the time comes, the James Webb will fly aboard an Ariane 5 rocket from the European Space Agency (ESA) launch facility near the town of Korou, French Guayana. Overnight on August 17th, 2021, the upper stage of that Ariane 5 began making its way in its cargo container from the ArianeGroup facility in Bremen, Germany, to Neustadt port, where it will board a ship bound for the ESA spaceport in French Guiana.
Artist’s impression depicting the separation of the ExoMars 2016 entry, descent and landing demonstrator module, named Schiaparelli, from the Trace Gas Orbiter, and heading for Mars. Credit: ESA/D. Ducros
In March of 2016, the European Space Agency (ESA) launched the ExoMars (Exobiology on Mars) mission into space. A joint project between the ESA and Roscosmos, this two-part mission consisted of the Trace Gas Orbiter (TGO) and the Schiaparelli lander, both of which arrived in orbit around Mars in October of 2016. While Schiaparelli crashed while attempting to land, the TGO has gone on to accomplish some impressive feats.
For example, in March of 2017, the orbiter commenced a series of aerobraking maneuvers, where it started to lower its orbit to enter Mars’ thin atmosphere and slow itself down. According to Armelle Hubault, the Spacecraft Operations Engineer on the TGO flight control team, the ExoMars mission has made tremendous progress and is well on its way to establishing its final orbit around the Red Planet.
TGO’s mission has been to study the surface of Mars, characterize the distribution of water and chemicals beneath the surface, study the planet’s geological evolution, identify future landing sites, and to search for possible biosignatures of past Martian life. Once it has established its final orbit around Mars – 400 km (248.5 mi) from the surface – the TGO will be ideally positioned to conduct these studies.
Visualization of the ExoMars mission’s Trace Gas Orbiter conducting aerobraking maneuvers to March of 2018. Credit: ESA
The ESA also released a graphic (shown above) demonstrating the successive orbits the TGO has made since it began aerobraking – and will continue to make until March of 2018. Whereas the red dot indicates the orbiter (and the blue line its current orbit), the grey lines show successive reductions in the TGO’s orbital period. The bold lines denote a reduction of 1 hour while the thin lines denote a reduction of 30 minutes.
Essentially, a single aerobraking maneuver consist of the orbiter passing into Mars’ upper atmosphere and relying on its solar arrays to generate tiny amounts of drag. Over time, this process slows the craft down and gradually lowers its orbit around Mars. As Armelle Hubault recently posted on the ESA’s rocket science blog:
“We started on the biggest orbit with an apocentre (the furthest distance from Mars during each orbit) of 33 200 km and an orbit of 24 hr in March 2017, but had to pause last summer due to Mars being in conjunction. We recommenced aerobraking in August 2017, and are on track to finish up in the final science orbit in mid-March 2018. As of today, 30 Jan 2018, we have slowed ExoMars TGO by 781.5 m/s. For comparison, this speed is more than twice as fast as the speed of a typical long-haul jet aircraft.”
Earlier this week, the orbiter passed through the point where it made its closest approach to the surface in its orbit (the pericenter passage, represented by the red line). During this approach, the craft dipped well into Mars’ uppermost atmosphere, which dragged the aircraft and slowed it down further. In its current elliptical orbit, it reaches a maximum distance of 2700 km (1677 mi) from Mars (it’s apocenter).
Visualization of the ExoMars Trace Gas Orbiter aerobraking at Mars. Credit: ESA/ATG medialab
Despite being a decades-old practice, aerobraking remains a significant technical challenge for mission teams. Every time a spacecraft passes through a planet’s atmosphere, its flight controllers need to make sure that its orientation is just right in order to slow down and ensure that the craft remains stable. If their calculations are off by even a little, the spacecraft could begin to spin out of control and veer off course. As Hubault explained:
“We have to adjust our pericentre height regularly, because on the one hand, the martian atmosphere varies in density (so sometimes we brake more and sometimes we brake less) and on the other hand, martian gravity is not the same everywhere (so sometimes the planet pulls us down and sometimes we drift out a bit). We try to stay at about 110 km altitude for optimum braking effect. To keep the spacecraft on track, we upload a new set of commands every day – so for us, for flight dynamics and for the ground station teams, it’s a very demanding time!”
The next step for the flight control team is to use the spacecraft’s thrusters to maneuver the spacecraft into its final orbit (represented by the green line on the diagram). At this point, the spacecraft will be in its final science and operation data relay orbit, where it will be in a roughly circular orbit about 400 km (248.5 mi) from the surface of Mars. As Hubault wrote, the process of bringing the TGO into its final orbit remains a challenging one.
“The main challenge at the moment is that, since we never know in advance how much the spacecraft is going to be slowed during each pericentre passage, we also never know exactly when it is going to reestablish contact with our ground stations after pointing back to Earth,” she said. “We are working with a 20-min ‘window’ for acquisition of signal (AOS), when the ground station first catches TGO’s signal during any given station visibility, whereas normally for interplanetary missions we have a firm AOS time programmed in advance.”
Artist’s impression of the ESA’s Exomars 2020 rover, which is expected to land on the surface of Mars by the Spring of 2o21. Credit:ESA
With the spacecraft’s orbital period now shortened to less than 3 hours, the flight control team has to go through this exercise 8 times a day now. Once the TGO has reached its final orbit (by March of 2018), the orbiter will remain there until 2022, serving as a telecommunications relay satellite for future missions. One of its tasks will be to relay data from the ESA’s ExoMars 2020 mission, which will consist of a European rover and a Russian surface platform being deployed the surface of Mars in the Spring of 2021.
Along with NASA’s Mars 2020 rover, this rover/lander pair will be the latest in a long line of robotic missions looking to unlock the secrets of Mars past. In addition, these missions will conduct crucial investigations that will pave the way for eventual sample return missions to Earth, not to mention crewed to the surface!
