Meet the dozens of space 'bots who spy on Earth, and why
Meteorologist/Science Writer
Thursday, September 28, 2017, 11:06 AM - Cassini is gone, and gone with it are the daily updates from Saturn, featuring amazing new images of the planet, its rings and the dozens of moons orbiting it. So now what? What can fill the gap left by the ending of this incredibly successful mission?
Look no further!
While the loss of Cassini was tough on those of us who are passionate about space and space exploration, it isn't the only space robot in the business of providing us with tours of our solar system.
There are plenty of other robots out there that regularly send back imagery. Starting with Earth and working our way outward, here's where to find them
LOW-EARTH ORBIT
The above animation shows a number of NASA's Earth-observing satellite fleet. If you would like to see the pictures taken by these satellites, head to the NASA Worldview website, where you can peruse imagery from several of them, such as LandSat-9, Aqua, Terra, Suomi NPP, and more.
There are other spacecraft in low-Earth orbit that return regular imagery for us, as well. The NASA/ESA Hubble Space Telescope is constantly peering into the universe at one object or another, and while many of the images are tied up in scientific studies, which only become available when the data is published, we can see public images on both the SpaceTelescope.org and HubbleSite.org websites. NASA's Solar Dynamics Observatory, or SDO, takes multiple images of the Sun every hour of every day, covering multiple wavelengths of light to reveal different features, and these are available via NASA's SDO website.
To see LIVE video from low-Earth orbit, from the International Space Station, check out NASA's ISS HD Earth Viewing Experiment.
GEOSTATIONARY ORBIT
At roughly 36,000 kilometres from the surface, there is a ring of satellites in geostationary orbit - meaning that as they orbit the Earth, they remain above one part of the Earth at all times. Here, we find the GOES East, GOES West and GOES-16 satellites, which monitoring and send back data about the weather over North and South America. GOES East and GOES West are responsible for our day-to-day weather monitoring, with different satellites holding those positions, over time. Currently, GOES-13 occupies the GOES East position, and GOES-15 occupies the GOES West position (follow the links for images).
GOES-16 is the real game-changer, though, with advanced capabilities that far outstrip what the current operational satellites (at least those over North and South America) are capable of.
The GOES-16 web portal provided by the Regional and Mesoscale Meteorology Branch of the Cooperative Institute for Research in the Atmosphere (CIRA) at Colorado State University. The animation flips through just five of the many views the satellite offers. Credit: RMMB/CIRA/CSU
Daily imagery from GOES-16 can be accessed through the RMMB/CIRA website.
Once GOES-16 has been fully tested and is ready to take on operational duty (sometime soon!), NOAA will move it into the GOES East position and put GOES-13 into standby mode as a backup.
THE MOON
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There are currently four different spacecraft still operating in lunar orbit.
Hands down, the best one for seeing regular (and amazing) imagery of the Moon, though, is NASA's Lunar Reconnaissance Orbiter (LRO). Launched in June 2009, LRO has since been returning close-up pictures of the lunar surface, its terrain features and even the various Apollo landing sites.
Follow the above link for an archive of individual images, or use the LRO Quickmap, shown to the right, which includes a 3D interactive map (switch views via the "projections" icon, top left).
LAGRANGE POINTS
In addition to the satellites directly orbiting Earth and the Moon, there are several that orbit around points nearby, but outside the Earth-Moon system. These points, known as Lagrange 1 (L1) and Lagrange 2 (L2), are points of stable gravity, formed by the interaction between the Sun and Earth, where spacecraft can maintain an orbit that follows along precisely with Earth, but is well away from the planet.
The Lagrange points of the Earth-Sun system, with the various spacecraft parked at both L1 and L2. Credit: NASA/Scott Sutherland
The satellites at L1 are (in chronological order) the Advanced Composition Explorer (ACE), Wind, the Solar and Heliospheric Observatory (SOHO) and the Deep Space Climate Observatory (DSCOVR). These are all there to monitor and study the Sun, solar activity and space weather, but a few added missions on the side.
While space weather data from ACE, Wind, SOHO and DSCOVR can be found on the NOAA Space Weather Prediction Center website, we can also view regular imagery of the Sun and the solar corona on NASA's SOHO website, and images of Earth from DSCOVR's Earth Polychromatic Imaging Camera (EPIC).
Each day, EPIC snaps several images of the daylight side of Earth, as the planet rotates beneath it. The full database of these images are available, going back to EPIC's first light in June of 2015, via the NASA EPIC browser.
NASA EPIC web interface, showing views of Earth from Sept 20, 2017. Hurricane Maria is clearly visible, as it impacts on Puerto Rico, and Tropical Storm Jose can be seen off the US east coast. Also visible - sunglint on the Pacific Ocean, Saharan dust over the eastern central Atlantic ocean, and smoke blanketing the Amazon rain forest. Credit: NASA
Note that the Moon only enters DSCOVR's view once in awhile, due to the angle of the Moon's orbit, with respect to Earth, and the relative position of the spacecraft around the L1 point in space. On most orbits, the Moon passes just above or just below EPIC's frame of view.
Out at L2, just beyond the tip of Earth's shadow, half a dozen spacecraft have orbited there, performing various tasks and studies. Five of those have either been decommissioned (WMAP, Herschel and Planck), moved to L1 (Wind) or continued on to another target (Chang'e 2). Only one is currently operating - the ESA's Gaia observatory, which is cataloguing stars in the Milky Way so that we can plot a 3D map of the entire galaxy. Check the ESA's website for images from Gaia's mission so far.
Near-Earth Asteroids
NASA and the Japan Aerospace Exploration Agency (JAXA) have both launched missions targetting near-Earth asteroids.
Hayabusa 2 (JAXA) is expected to reach asteroid (162173) Ryugu in June 2018. Updates from the mission can be found here, including the beautiful image of Earth it took on December 4, 2015, during its gravity assist flyby. Watch for more to come as the spacecraft nears its target.
OSIRIS-REx (NASA), which launched in September 2016, en route for an approach to asteroid Bennu in August of 2018, has already snapped pictures while looking for any Earth Trojan asteroids, and it recently performed an Earth gravity assist, where it captured the following picture of our planet:
Earth's Pacific Ocean, Australia and western North America are clearly visible in this image, taken by OSIRIS-REx's MapCam camera, on Sep 22, 2017. The black lines at the top of the image are artifacts of the short exposure time for the images, due to Earth's brightness. Credit: NASA's Goddard Space Flight Center/University of Arizona
Venus
Even with its proximity to Earth, Venus is far less studied than we'd like. Partly to blame is the thick cloud cover that surrounds the planet. Since it's impossible to snap visible images of the surface directly from space, there has been less incentive to send exploration missions there. Also, with the adverse conditions on the surface (to put it mildly) landing anything on the planet means having a very short mission duration, indeed.
The only missions to send back images from the surface - Soviet Venera 9, 10, 13 and 14 - all burned out long ago. Others, such as NASA's Pioneer Venus Orbiter, the Magellan probe, and even the Galileo spacecraft (during its Venus gravity assist), have returned images of the clouds and radar imagery of the surface features. The images and data from all of these missions is available on the NASA Space Science Data Coordinated Archive (NSSDCA) photo gallery.
Currently, Japan's Venus Climate Orbiter "AKATSUKI" is the only spacecraft actively investigating Venus. Mission updates (in English), with images, are available here.
Mars
Besides Earth, Mars is the most well-explored planet in our solar system, so far. Several landers and rovers have examined its surface, along with a number of orbiters supporting them and taking images of their own.
The above animation shows the locations of the landers and rovers on the surface, and most of the spacecraft currently orbiting the planet. Missing is the ESA's ExoMars Trace Gas Orbiter (TGO), which arrived in October 2016.
Only one rover is still operating today - NASA's Mars Science Laboratory Curiosity. Mars Exploration Rover (MER) Opportunity may still come back and communicate with Earth, but it has been down since June 2018, due to the effects of a global dust storm. Both of these rovers sent back data and images on a regular basis, and Curiosity still does. Opportunity's full database of raw imagery can be accessed through NASA's website. (Opportunity's twin, Spirit, stopped transmitting in 2010, but its database of raw images can be found here).
Images taken by the various cameras on Curiosity are also accessible online (example shown below), and NASA has compiled a gallery of favourites for the public to peruse, as well.
Mars rover Curiosity's raw image web interface, organized by "Sol" (Mars day). Credit: NASA/JPL-Caltech
There is also a new lander on the planet - Mars InSight. The robot's raw image database can be accessed from NASA's Mars mission website.
Mars from space is just as spectacular, possibly even more so, and images from the various spacecraft can be found on their respective websites:
• NASA's Mars Reconnaissance Orbiter (MRO), Mars Odyssey and MAVEN.
• ESA's Mars Express and ExoMars TGO.
• India's Mars Orbiter Mission (MOM).
THE ASTEROID BELT
NASA's NEOWISE mission, along with various Earth-based sky surveys, are constantly scanning for new asteroids and comets. While the data they accumulate rarely include photos, updates of the asteroid count can be found on the NEOWISE website and the International Astronomical Union's Minor Planet Center.
The two largest asteroids in the asteroid belt, dwarf planet Ceres and asteroid 4 Vesta, were just points of light in the night sky until NASA's Dawn mission arrived to map their surfaces (4 Vesta in July 2011 and Ceres in March 2015).
Dawn's images are available via the NASA JPL image gallery.
The Sun
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In addition to the two solar missions close to Earth - SDO and SOHO - there are two other space probes that have kept a constant watch on the Sun, but from the far side.
The twin STEREO spacecraft - STEREO-A and STEREO-B - work to give us advanced notice of sunspots and solar activity. The imagery of these two, combined with SDO and SOHO, providing us with full 360 degree view of the Sun, at all times.
Unfortunately, NASA lost contact with STEREO-B in 2014, due to an anomaly with the spacecraft's computer, and although they were able to briefly re-establish contact in August 2016, the probe is still not sending any imagery or data back to us.
STEREO-A still sends back regular data, however, which can be viewed on the STEREO Science Center website.
JUPITER
Jupiter has been a favourite target of missions, both those headed directly to the gas giant and those headed for destinations beyond. Thus, there are plenty of images of the planet and its moons out there, captured by Pioneers 10 and 11, Voyagers 1 and 2, Galileo, Cassini, New Horizons, and most recently Juno.
NASA's Juno spacecraft pulled into orbit around Jupiter on July 4, 2016, and the images we've seen since have been amazing! Not only is NASA providing the images in their raw format, so that citizen scientists with a flare for image processing can piece them together and coax out as much detail as possible, but they also have an open system of voting for what Juno's imaging targets will be on each pass it makes over the planet's cloud-tops.
A sample of Juno's raw image database, with pics taken by JunoCam on Sep 1, 2017. Credit: NASA/SwRI/MSSS
If you'd like to have a say in where the spacecraft points its camera on upcoming encounters, head to the Southwest Research Institute website.
OUTER SOLAR SYSTEM
With Cassini's mission over, the only space probes we have beyond Jupiter are either no longer sending back images (Pioneers 10 and 11, and Voyagers 1 and 2), or they are still on approach to their next target.
Voyagers 1 and 2 are now considered to be in interstellar space, as they have flown beyond the edge of the Sun's heliosphere. Both probes are still sending back data from their passive sensors (Voyager 2, more than Voyager 1), so they still have plenty to teach us about the environment surrounding our solar system.
New Horizons gave us a spectacular close-up views of binary planet Pluto and Charon, along with their collection of tiny moons, back in July 2015. Now, it is speeding on through the Kuiper belt after its January 1st encounter with peanut-shaped contact-binary KBO, 2014 MU69.
An image of 2014 MU69, snapped by New Horizons' Long-Range Reconnaissance Imager (LORRI), on January 1, 2019, at a distance of just 28,000 kilometers. At this resolution, each pixel of the image is 140 meters on a side. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Even though the flyby is over, data from this encounter will be downlinking for months, so watch for more to come from this mission, coming up!
Sources: NASA | JPL-Caltech | NOAA | JAXA | ESA | Southwest Research Institute | Arizona State University
