Space junk is a growing problem. For decades we have been sending satellites into orbit around Earth. Some of them de-orbit and burn up in Earth’s atmosphere, or crash into the surface. But most of the stuff we send into orbit is still up there.
This is becoming an acute problem as years go by and we launch more and more hardware into orbit. Since the very first satellite—Sputnik 1—was launched into orbit in 1957, over 8000 satellites have ben placed in orbit. As of 2018, an estimated 4900 are still in orbit. About 3000 of those are not operational. They’re space junk. The risk of collision is growing, and scientists are working on solutions. The problem will compound itself over time, as collisions between objects create more pieces of debris that have to be dealt with.
Let’s be honest, launching things into space with rockets is a pretty inefficient way to do things. Not only are rockets expensive to build, they also need a ton of fuel in order to achieve escape velocity. And while the costs of individual launches are being reduced thanks to concepts like reusable rockets and space planes, a more permanent solution could be to build a Space Elevator.
And while such a project of mega-engineering is simply not feasible right now, there are many scientists and companies around the world that are dedicated to making a space elevator a reality within our lifetimes. For example, a team of Japanese engineers from Shizuoka University‘s Faculty of Engineering recently created a scale model of a space elevator that they will be launching into space tomorrow (on September 11th).
Stand outside and take deep breath. Do you know what you’re breathing? For most people, the answer is simple – air. And air, which is essential to life as we know it, is composed of roughly twenty-percent oxygen gas (O²) and seventy-eight percent nitrogen gas (N²). However, within the remaining one-percent and change are several other trace gases, as well as few other ingredients that are not always healthy.
When it comes to space exploration, the motto “keep it simple” isn’t always followed! For the most part, satellites, spacecraft, telescopes, and the many other technologies that allow humans to study and explore the Universe are the result of highly-technical and complex feats of engineering. But sometimes, it is the simplest ideas that offer the most innovative solutions.
This is especially true when it comes to the today’s space agencies, who are concerned with cutting costs and increasing accessibility to space. A good example is the Fenix propulsion system, a proposal created by Italian tech company D-Orbit. As part of the last year’s Space Exploration Masters, this pen-sized booster will allow CubeSats to maneuver and accomplish more in space.
The Space Exploration Masters, which the European Space Agency (ESA) initiated in 2017, seeks to encourage space-based innovation and provide opportunities for commercial development. As such, this annual competition has become central to the implementation of the ESA Space Exploration strategy. For their application last year, D-Orbit was jointly awarded the the ESA and Space Application Services prize.
The thruster prototype itself measures only 10 cm long and 2 cm wide (~4 by 0.8 inches) and contain solid propellant that is triggered by a simple electrical ignition system. The boosters are designed to be placed at each corner of a 10 x 10 x 10 cm CubeSat, or can be doubled up for added thrust. Thanks to their lightweight and compact size, they do not take up much instrument space or add significantly to a CubeSat’s weight.
Currently, CubeSats are deployed directly into space, deorbit at the end of their missions, and have no means to change their orbits. But with this simple, chemical-propellant thruster, CubeSats could function for longer periods and would be able to take on more complicated missions. For instance, if they can maneuver in orbit, they will be able to study the Moon and asteroids from different angles.
In addition, boosters will allow CubeSats to deorbit themselves once they are finished their missions, thus reducing the threat of space debris. According to the latest report from the Space Debris Office at the European Space Operations Center (ESOC), an estimated 19,894 bits of space junk were circling our planet by the end of 2017, with a combined mass of at least 8135 metric tons (8967 US tons). This problem is only expected to get worse.
In fact, it is estimated that the small satellite market will grow by $5.3 billion in the next decade (according to Space Works and Eurostat) and many private companies are looking to provide regular launch services to accommodate that growth. As such, a propulsion system that not only presents opportunities to do more with CubeSats, but in a way that will not add to problem of space debris, will be highly sought-after.
In addition to the ESA and Space Application Services prize, D-Orbit won a four-month ticket to test their prototype on the newly-installed ICE Cubes facility, which is located in the Columbus module aboard the International Space Station. This facility is the first European commercial research center to operate aboard the ISS, and the D-Orbit team will use to test the booster’s safe ignition mechanism inside an ICE cube experiment.
This experiment, which will not involve firing the actual propulsion system, will help ensure that the booster can operate safe and effectively in space. Sensors and cameras will record the sparks, triggered by an electrical impulse, while the team relies on the ICE Cubes facility’s dedicated control center to provide them with remote viewing opportunities from the ground.
The Fenix boosters are set to launch for the ISS by the end of next year and, if successful, D-Orbit will likely secure permission to test their propulsion system in space. And if all goes well, future generations of CubeSats – which have already made Low Earth Orbit (LEO) accessible to private companies and research institutes – will be capable of performing far more tasks in orbit.
For this year’s Space Exploration Masters, the ESA is partnering with the United Nations World Health Organization (WHO) to address health and food. For the main challenge, participants will be tasked with coming up with applications that promote nutritious food and food security, both on- and 0ff-planet. Among other challenges, this year’s SEM will also be looking for ideas that make missions more sustainable and new ways to use future spacecraft.
For more information on this year’s Space Exploration Masters, check out the ESA website page.
Are you ready for a luxury hotel in space? We all knew it was coming, even though it seems impossibly futuristic. But this time it’s not just science fiction; somebody actually has a plan.
The space hotel will be called “Aurora Station” and the company behind it is Orion Span, a Silicon Valley and Houston-based firm. Orion Span aims to deliver the astronaut experience to people, by delivering the people into space. The catch?
“We developed Aurora Station to provide a turnkey destination in space. Upon launch, Aurora Station goes into service immediately, bringing travelers into space quicker and at a lower price point than ever seen before, while still providing an unforgettable experience” – Frank Bunger, CEO and founder of Orion Span.
First of all, a 12 day stay aboard Aurora Station for two people will cost $19 million US, or $9.5 million per person. Even so, you can’t just buy a ticket and hop on board. Guests must also sign up for three months of Orion Span Astronaut Certification (OSAC). Then they’ll be trained at a facility in Houston, Texas.
So once their cheque has cleared, and once they’re trained, what awaits guests on Aurora Station?
Aurora Station will orbit Earth at 320 km (200 m) and will make the trip around Earth every 90 minutes. If you do the math, that’s 16 sunrises and sunsets each day, and guests will enjoy this slideshow for 12 days. Other than this compressed schedule of 96 sunsets and 96 sunrises during their 12 day stay, guests will also be treated to stunning views of the Earth rolling by underneath them, thanks to the unprecedented number of windows Aurora Station will have.
Aurora Station is the brain-child of Orion Span’s CEO, Frank Bunger. “We developed Aurora Station to provide a turnkey destination in space. Upon launch, Aurora Station goes into service immediately, bringing travelers into space quicker and at a lower price point than ever seen before, while still providing an unforgettable experience,” said Bunger.
Guests won’t be alone on the station, of course. The space hotel will have room for 6 people in total, meaning 4 guests and 2 crew. (You didn’t think you’d be alone up there, did you?) Each pair of guests will still have some alone time though, in what Orion Span calls luxurious private suites for two.
There’s no doubt that staying on a space hotel for 12 days will be the experience of a lifetime, but still, 12 days is a long time. The space station itself will be 5600 square feet, with two suites that can be configured to four. Each suite will be about the size of a small bedroom. Once you’ve gotten used to seeing Earth below you, and you’re used to your suite, what will you do?
Well, there’ll be Wi-Fi of course. So if you’re the type of person who gets bored of orbiting the only planet that we know of that hosts life, and the only planet on which every human civilization has lived and died on, you can always surf the web or watch videos. Aurora Station will also have a virtual-reality holodeck, the cherry-on-top for this science-fiction-come-to- life space resort.
But apparently, boredom won’t be a problem. In an interview with the Globe and Mail, Orion Span CEO Frank Bunger said, ““We talked to previous space tourists, they said 10 days aboard the space station was not enough.” Maybe the extra 2 days in space that Aurora Station guests will enjoy will be just the right amount.
As far as getting guests to the station, that will be up to other private space companies like SpaceX. SpaceX has plans to send tourists on trips around the Moon, and they have experience docking with the International Space Station, so they should be able to transport guests to and from a space hotel.
It doesn’t seem like there’s any shortage of customers. Aurora Station was introduced on April 5th 2018, and the first four months of reservations sold out within 72 hours, with each guest paying a deposit of $80,000 US.
There’s another side to Aurora Station, though. Other than just a nice get-away for people who can afford it, there’s a research aspect to it. Orion Span will offer Aurora Station as a platform for micro-gravity research on a pay-as-you-go basis. It will also lease capacity for in-situ manufacturing and 3D printing research.
But Aurora Station would hardly be in the news if it was only a research endeavour. What’s got people excited is the ability to visit space. And maybe to own some real estate there.
Orion Span is designing Aurora Station to be expandable. They can attach more stations to the original without disrupting anything. And this leads us to Orion Span’s next goal: space condos.
As it says on Orion Span’s website, “Like a city rising from the ground, this unique architecture enables us to build up Aurora Station in orbit dynamically – on the fly – and with no impact to the remainder of Aurora Station. As we add capacity, we will design in condos available for purchase.”
I think we all knew this would happen eventually. If you have the money, you can visit space, and even own a condo there.
Okay, if you’ve got some spare time, check out this amazing website called Stuff in Space. It’s a simulation of every satellite (alive or dead), space station, and large piece of space junk orbiting the Earth right now.
You can zoom in and out, rotate the Earth and its satellites around. Pick any one object and discover more information about it. Or just leave it running and watch all the objects buzz around in real time. Humans have been busy launching a lot of stuff, and it’s only going to increase.
The simulation was made by James Yoder, an incoming Electrical and Computer Engineering freshman at the University of Texas at Austin, and it’s based on data supplied by Space Track, which is a service of the Joint Space Operations Center. They have a bunch of handy data feeds and APIs that you can use track orbital objects, but I’ve never seen anything as creative as this.
One of the technological hurdles of our age is to get people and equipment into space more cheaply. SpaceX gets a lot of the headlines around that, with their reusable rockets. And so does Blue Origin, to some degree. Now a small start-up affiliated with Purdue University is tackling the problem and making some headway.
The company is called Leo Aerospace LLC and they’re using balloons to lower the cost of putting micro-satellites into orbit, rather than reusable rockets. The balloons will be reusable, but the rockets won’t.
Leo Aerospace plans to revive a decades-old method of putting satellites into space. They’re using hot air balloons to lift the rocket and its micro-satellite payload 18 km (11 miles) above Earth. At that altitude, there’s 95% less atmosphere. This means much less drag on the rocket, which translates into smaller rockets with less fuel. This is an intriguing idea, if not for the unfortunate name.
The rockoons will be used to launch rockets into sub-orbital and orbital flights. Sub-orbitals are often used by researchers because it gives them access to zero gravity and to vacuum, both of which are necessary for some experiments. According to Leo Aerospace, there’s something revolutionary about their plans.
“We’re targeting the microsatellites by saying, ‘You don’t have to ride-share with anyone. We can guarantee you will be our only payload and we will be focused on you.’” – Drew Sherman, Leo Aerospace’s Head of Vehicle Development.
They intend on targeting micro-satellite developers. Micro-satellites are often hitch-hikers on larger payloads, which basically means they’re second-class customers. They have to wait until there’s room for their micro-satellite on a traditional rocket carrying a larger payload. This can mean long delays of several months, and that micro-satellite developers have to compromise when it comes to the orbits they can obtain. It can also make micro-satellite missions difficult to plan and execute efficiently and economically. Micro-satellites are becoming more and more capable, so having a launch system tailor-made for them could indeed be revolutionary.
“We’re targeting the microsatellites by saying, ‘You don’t have to ride-share with anyone. We can guarantee you will be our only payload and we will be focused on you,’” said Drew Sherman, Leo Aerospace’s head of vehicle development. “‘We will work with you exclusively to get you into orbit. You won’t have to worry about other payloads or getting dropped off in the wrong spot.’”
The flexibility of the rockoon system that Leo Aerospace is developing will be intriguing for micro-satellites. Rockoons will give micro-satellites the flexibility they need to operate efficiently. The launch can be scheduled and adapted to the needs of the individual satellite. “Our goal is to give people access to space. The only way to do that right now is to help people get their satellite into orbit. That’s where we want to leave our mark,” said Abishek Murali, Head of Mission Engineering at Leo Aerospace.
“Our goal is to give people access to space.” – Abishek Murali, Head of Mission Engineering at Leo Aerospace
The rockoon itself is a hybrid of a balloon and a rocket. The hybrid design takes advantage of physics by using the balloon to float the rocket 18 km high before launching the rocket. The rockoon has Leo Aerospace’s own patent-pending technology to control the pitch and angle of the launch, allowing for precision launches.
Rockoons were first used by the US Air Force back in the 1950s. But this next generation of rockoons, coupled with modern micro-satellites, will be much more capable than the 1950s technology.
Currently, Leo Aerospace is in the development and funding phase. They’ve obtained some funding from the National Science Foundation, and from a venture capital firm. They have about half of the $250,000 they need. They plan to conduct their first sub-orbital flight in 2020, and to launch their first micro-satellite into orbit in 2022. They intend to use existing approved launch sites.
Leo Aerospace was founded by five then-students at Purdue University. Leo started as a club, but the former students have turned it into a business. And that business seems to have a bright future. They conducted a customer discovery and market validation study and found a large demand for a better way to launch micro-satellites.
“We want to be part of the space market,” Murali said. “People are interested in space and creating technologies that not only can operate in space but also help people back on Earth. What we’re trying to do is help them get there.”
But they still need a better name than “rockoons.”
I apologize for the end-of-the-world title, but everything in it is true. And the world will still be here after it’s all done. On Friday (March 31) at 7:36 a.m. Central Time, the Moon will be full for the second time this month, which makes it a Blue Moon according to popular usage. Enjoy it. What with January’s Blue Moon and now this, we’ve chewed through all our Blue Moons till Halloween 2020.
I look forward to every full moon. Watching a moonrise, we get to see all manner of amazing atmospheric distortions play across the squat, orange disk. Once the sky’s dark, its outpouring of light makes walking at night a pleasure.
When a full moon occurs in spring, it hurries south down the ecliptic, the imaginary circle in the sky defining Earth’s orbit around the Sun. For northern hemisphere skywatchers, this southward sprint delays its rising by more an hour each night, forcing a quick departure from the evening sky. And that means blessed darkness for hunting down favorite galaxies and star clusters.
Tiangong 1 and a reentry simulation
As the Moon rolls along, the hapless Chinese space station Tiangong 1 hurtles toward Earth. Drag caused by friction with the upper atmosphere continues to shrink the spacecraft’s orbit, bringing it closer and closer to inevitable breakup and incineration. Since the Chinese National Space Administration (CNSA) lost touch with Tiangong 1 in March 2016, mission control can no longer power thrusters to de-orbit it at chosen time over a safe location like the ocean. The 9.3-ton (8,500 kg) station will burn up somewhere anywhere over a vast swath of the planet between latitudes 43°N and 43°S. Included within this zone are the southern half of Europe, the southern two-thirds of the U.S., India, Australia and much of Africa and South America.
Not until the day of or even hours before will have a clear idea of when and where the station will meet its fate. According to the latest update from the Aerospace Corp., which monitors falling spacecraft, reentry is expected on Easter Sunday (April 1) at 10:30 UT / 5:30 a.m. Central Time plus or minus 16 hours. This morning (March 29), the space station is circling Earth at about 118 miles (190 km) altitude. The lowest a satelllite can still make a complete orbit of the planet is about 62 miles (100 km). Below that, break-up begins.
For up-to-the-minute updates on when to expect Tiangong 1’s orbit to decay and the machine to plunge to Earth, check out Joseph Remis’ Twitter page. Most of the space station is expected to burn up on reentry, but larger chunks might survive all the way to the ground. Since much more of the Earth’s surface is water these remnants will likely end up in the drink … but you never know. If Tiangong-1 does come down over a populated area, observers on the ground will witness a spectacular, manmade fireball day or night.
On the quieter side but nearly as eye-catching, Mars will overtake Saturn in the coming week, passing just 1° south of the ringed planet in a thrilling dawn conjunction on April 2. If the weather forecast doesn’t look promising that morning, the two planets will remain within 2° of each other now through April 6th, providing plenty of opportunities for a look.
You can easily tell them apart by color: Mars is distinctly red-orange and Saturn looks creamy white. Both are bright at around magnitude 0 though Mars is now a hair brighter by two-tenths of a magnitude. Will you be able to see the difference?
In most telescopes at low magnification both planets will comfortably fit in the same field of view. Saturn’s rings are tilted nearly wide open and quite beautiful. Mars appears gibbous and though still rather small, it’s brightening rapidly and drawing closer in time for its closest approach to Earth since 2003. Wishing you clear skies!
After multiple delays, SpaceX’s PAZ mission launched from from Space Launch Complex 4 East (SLC-4E) at Vandenburg Air Force Base on the morning of Thursday, February 22nd. Shortly after it reached orbit, the rocket deployed its payload (the PAZ Earth Observing satellite) as well as and two Starlink demonstrations satellites that will test SpaceX’s ability to provide broadband internet service from orbit.
In addition, this launch was the first time that SpaceX would be attempting to “catch” the payload fairings from a Falcon 9 rocket using a retrieval ship. As part of their plan to make their rockets fully reusable, the rocket’s fairings were equipped with deployable chutes that would control their descent to the Pacific Ocean. Once there, the newly-commissioned “Mr. Steven” retrieval ship would be waiting to catch them in its net.
As noted, the primary mission for this launch was the deployment of the the PAZ satellite to low-Earth orbit. This synthetic-aperture radar satellite was commisioned by Hisdesat, a Spanish commercial satellite company, for governmental and commercial use. Its purpose s to generate high-resolution images of the Earth’s surface, regardless of whether there are clouds covering the ground.
https://www.instagram.com/p/BfgHKDNAplx/
The secondary payload consisted of two experimental satellites – Microsat-2a and 2b – which are the first phase in SpaceX’s plan to deliver broadband internet service to the entire world. The plan calls for the deployment of more satellites in phases, reaching a total of 4,000 by 2024. However, it was the attempted retrieval of the rocket’s payload fairings that was of particular interest during the launch.
To be fair, this would not be the first time that SpaceX’s attempted to retrieve payload fairings. In March of 2017, SpaceX successfully recovered the fairings for one of their Falcon 9s, which allowed them to recoup an estimated $6 million dollars from that launch. At present, SpaceX indicates that the cost of an individual Falcon 9 launch is estimated to be around $62 million.
If the payload fairings could be recovered regularly, that means that the company could stand to recoup an additional 10% from every individual Falcon 9 launch. These additional savings would not only make the company more competitive, but could allow for additional mission profiles that are currently considered too expensive.
Missed by a few hundred meters, but fairing landed intact in water. Should be able catch it with slightly bigger chutes to slow down descent.
On Thursday Morning, SpaceX founder Elon Musk posted a picture of Mr. Steven taking to sea on Instagram with the following statement:
“Going to try to catch the giant fairing (nosecone) of Falcon 9 as it falls back from space at about eight times the speed of sound. It has onboard thrusters and a guidance system to bring it through the atmosphere intact, then releases a parafoil and our ship with basically a giant catcher’s mitt welded on tries to catch it.”
The launch, which was covered via webcast, went as planned. After taking off amid clear skies, the Falcon 9 reached orbit and deployed the PAZ satellite without incident, and the two Starlink satellites were deployed shortly thereafter. However, the webcast ended without providing any information about the status of the retrieval of the payload fairings.
At 7:14 am, Musk tweeted an update about the attempted retrieval, indicating that the fairings had landed in the ocean a few hundred meters from where Mr. Steven was waiting to catch them. While unsuccessful, Musk was optimistic about future attempts to retrieve payload fairings, saying:
“Missed by a few hundred meters, but fairing landed intact in water. Should be able catch it with slightly bigger chutes to slow down descent.”
As always, Musks seems undeterred by a setback and the company is moving ahead with its plans for expanded reusability. If successful, future attempts at retrieval are likely to involve the second stages of the Falcon 9 and Falcon Heavy rockets. Given all the possibilities that this will allow for, there are many who want to see Musk’s latest venture to succeed.
In the meantime, check out this webcast of the launch:
One of the most visible signs of Climate Change are the ways in which glaciers and ice sheets have been disappearing all over the world. This trend is not reserved to the Arctic ice cap or the Antarctic Basin, of course. On every part of the planet, scientists have been monitoring glaciers that have been shrinking in the past few decades to determine their rate of loss.
These activities are overseen by NASA’s Earth Observatory, which relies on instruments like the Landsat satellites to monitor seasonal ice losses from orbit. As these satellites demonstrated with a series of recently released images, the Puncak Jaya ice sheets on the south pacific island of Papua/New Guinea have been receding in the past three decades, and are at risk of disappearing in just a decade.
The Papau province of New Guinea has a very rugged landscape that consists of the mountains that make up Sudirman Range. The tallest peaks in this range are Puncak Jaya and Ngga Pulu, which stand 4,884 meters (16,020 feet) and 4,862 meters (15,950 feet) above sea level, respectively. Despite being located in the tropics, the natural elevation of these peaks allows them to sustain small fields of “permanent” ice.
Given the geography, these ice fields are incredibly rare. In fact, within the tropics, the closest glacial ice is found 11,200 km (6,900 mi) away on Mount Kenya in Africa. Otherwise, one has to venture north for about 4,500 km (2,800 mi) to Mount Tate in central Japan, where glacial ice is more common since it is much farther away from the equator.
Sadly, these rare glaciers are becoming more threatened with every passing year. Like all tropical glaciers in the world today, the glaciers on the slopes around Puncak Jaya have been shrinking at a such a rate that scientists estimate that they could be gone within a decade. This was illustrated by a pair of Landsat images that show how the ice fields have shrunk over the past thirty years.
The first of these images (shown above) was acquired on November 3rd, 1988, by the Thematic Mapper instrument aboard the Landsat 5 satellite. The second image (shown below) was acquired on December 5th, 2017, by the Operational Land Imager (OLI) on the Landsat 8 satellite. These false-color images are a combination of shortwave infrared, infrared, near-infrared, and red light.
The extent of the ice fields are shown in light blue, whereas rocky areas are represented in brown, vegetation in green, and clouds in white. The gray circular area near the center of the 2017 image is the Grasberg mine, the largest gold and second-largest copper mine in the world. This mine expanded considerably between the 1980s and 2000s are a result of a boom in copper prices.
As the images show, in 1988, there were five masses of ice resting on the mountain slopes – the Meren, Southwall, Carstensz, East Northwall Firn and West Northwall Firn glaciers. However, by 2017, only the Carstensz and a small portion of the East Northwall Firn glaciers remained. As Christopher Shuman, a research professor at the University of Maryland Baltimore County and NASA’s Goddard Space Flight Center, explained:
“The ice area losses since the 1980s here are quite striking, visible in the contrast of the blue ice with the reddish bedrock. Even though the area still gets snowfalls, it is clearly not sustaining these glacial remnants.”
Similarly, in 2009, images taken by Landsat 5 of these same glaciers (see below) indicated that the Meren and Southwall glaciers had disappeared. Meanwhile, the Carstensz, East Northwall Firn and West Northwall Firn glaciers had retreated dramatically. Based on the rate of loss, scientists estimated at the time that all of Puncak Jaya’s glaciers would be gone within 20 years.
As these latest images demonstrate, their estimates were right on the money. At their current rate, what remains of the Carstensz and East Northwall Firn glaciers will be gone by the late 2020s. The primary cause of the ice loss is rising air temperatures, which leads to rapid sublimation. However, changes in humidity levels, precipitation patterns and cloudiness can also have an impact.
Humidity is also important, since it affects how readily glaciers can lose mass directly to the atmosphere. Where the air is more moist, ice is able to make the transition to water more easily, and can be returned to the glacier in the form of precipitation. Where the air is predominately dry, ice makes the transition directly from a solid form to a gaseous form (aka. sublimation).
Temperature and precipitation are also closely linked to ice loss. Where temperatures are low enough, precipitation takes the form of snow, which can sustain glaciers and cause them to grow. Rainfall, on the other hand, will cause ice sheets to melt and recede. And of course, clouds affect how much sunlight reaches the glacier’s surface, which results in warming and sublimation.
For many tropical glaciers, scientists are still working out the relative importance of these factors and attempting to determine to what extent anthropogenic factors plays a role. In the meantime, tracking how these changes are leading to ice loss in the tropical regions provides scientists with a means of comparison when studying ice loss in other parts of the world.
As Andrew Klein, a geography professor at Texas A & M University who has studied the region, explained:
“Glacier recession continues in the tropics—these happen to be the last glaciers in the eastern tropics. Fortunately, the impact will be limited given their small size and the fact that they do not represent a significant water resource.”
Satellites continue to play an important role in the monitoring process, giving scientist the ability to map glacier ice loss, map seasonal changes, and draw comparisons between different parts on the planet. They also allow scientists to monitor remote and inaccessible areas of the planet to see how they too are being affected. Last, but not least, they allow scientists to estimate the timing of a glacier’s disappearance.