Does The Earth's Magnetic Field Go Past The ISS?

Does the Earth’s magnetosphere encompass the ISS and does it offer the same protection as it does our atmosphere and planet?
A profile view of the magnetic field and density data. Image Credit: NASA's Scientific Visualization Studio, the Space Weather Research Center (SWRC), the Community-Coordinated Modeling Center (CCMC) and the Space Weather Modeling Framework (SWMF).

A profile view of the magnetic field and density data. Image Credit: NASA's Scientific Visualization Studio, the Space Weather Research Center (SWRC), the Community-Coordinated Modeling Center (CCMC) and the Space Weather Modeling Framework (SWMF).

Originally posted on Forbes!

The International Space Station, or ISS, orbits our planet once every 90 minutes at the lofty height of 400 kilometers (about 248 miles) above the surface of our planet. This altitude puts it pretty well above the vast majority of the atmosphere, but it doesn’t place it outside the reaches of the magnetic field which surrounds our Earth.

The International Space Station, in orbit around Earth. Image credit: Science@NASA and NASA’s Goddard Space Flight Center, International Space Station image courtesy of NASA

The International Space Station, in orbit around Earth. Image credit: Science@NASA and NASA’s Goddard Space Flight Center, International Space Station image courtesy of NASA

The magnetic field of our planet — otherwise known as the magnetosphere — extends out to about 65,000 kilometers (40,000 mi) above the surface of the planet. However, that “about” part is pretty critical — the magnetosphere isn’t a fixed boundary, which always remains at exactly 40,000 miles from the surface. This surface is a little more flexible, and if you’ve ever held two opposing magnet ends against each other, you’ve felt this exact flexibility. The resistance between two magnets isn’t a wall, where suddenly you can’t move them any closer to each other. The pressure there is a little more like pressing on a slightly under-inflated balloon.

In the case of the Earth’s magnetic field, the pressure on our magnetic field comes from the Sun. The Sun is constantly battering everything surrounding it with a solar wind, made up of charged particles. If you’re a planet without a protective magnetic field, this solar wind will slam into your atmosphere, and can destroy it over time. This is roughly what we believe happened to Mars’ atmosphere. The Earth has a very fortunate protective shield, but this constant pressure on the Sun’s side of our planet means that this magnetic protection is pressed back, closer to the planet. That 40,000 mile number I gave is this: the typical, Sun-compressed, Sun-facing side of our magnetosphere. The nighttime side of our planet, facing away from the Sun, has a long magnetic tail drifting out beyond it, extending several times farther out than the Sun-side.

A profile view of the magnetic field and density data during a solar outburst. Image Credit: NASA’s Scientific Visualization Studio, the Space Weather Research Center (SWRC), the Community-Coordinated Modeling Center (CCMC) and the Space Weather Modeling Framework (SWMF).

A profile view of the magnetic field and density data during a solar outburst. Image Credit: NASA’s Scientific Visualization Studio, the Space Weather Research Center (SWRC), the Community-Coordinated Modeling Center (CCMC) and the Space Weather Modeling Framework (SWMF).

If the Sun has a particularly strong outburst – a coronal mass ejection or any kind of solar flare — the pressure on our magnetic field gets much stronger, but nothing the Sun typically does will press the magnetic field down close enough to the Earth’s atmosphere so that the ISS would exit the magnetic field. Some of our highest orbiting satellites do exit the magnetic field of the Earth, as of course all craft going to other planets must also do. However, these satellites and spacecraft must be constructed to protect their inner workings from the charged particles in the solar wind. Satellites are effectively very elaborate electronics, and electronics do not like being exposed to charged particles. It shorts their circuits.

All this really means that the ISS is in a much safer region of space than it could be – not that it’s totally safe. Our magnetic field is not a perfect blocker of high energy particles, and so things like gamma rays, cosmic rays, and other damaging radiation can still appear in higher quantities than they would if the astronauts were still safely on  the ground. Our atmosphere is pretty good at blocking a lot of these high energy particles, so on the ground you’d never get exposed to them. But the ISS is above the atmosphere, and doesn’t have this extra layer of shielding, so there are radiation monitors on the space station to keep track of how much of a radiation dose they’re getting. If a solar flare is on its way, the astronauts usually have a few days’ warning, and can take shelter in more strongly shielded section of the ISS if they need to. (Not all solar storm are aimed in their direction, and not all storms are strong enough to require this precaution.)

So yes, the ISS is firmly embedded in the Earth’s magnetosphere, making it — for a space based outpost — a relatively safe haven for our astronauts.

Have your own question? Feel free to ask! Or submit your questions via the sidebar, Facebook, twitter, or Google+.

Sign up for the mailing list for updates & news straight to your inbox!

How Is There Internet On The Space Station?

What about the internet in the space station and NASA communication with spaceships??
The radio and satellite communications network allows ISS crews to talk to the ground control centers and the orbiter. It also enables ground control to monitor and maintain ISS systems and operate payloads, and it permits flight controllers to send commands to those systems. The network routes payload data to the different control centers around the world. Image credit: NASA

The radio and satellite communications network allows ISS crews to talk to the
ground control centers and the orbiter. It also enables ground control to monitor and
maintain ISS systems and operate payloads, and it permits flight controllers to send
commands to those systems. The network routes payload data to the different control
centers around the world. Image credit: NASA

Originally posted at Forbes!

We covered some of the tricks behind NASA’s communication with spaceships a little while back, but the International Space Station’s internet access is pretty interesting. There are some significant challenges with getting the internet set up in space, beginning with not being able to run a fiber-optic cable from ground to space, and we still don’t have a planetary scale wifi network yet, so getting a wifi hotspot in space is still a challenge.

The vast majority of communication with the ISS happens via radio. Radio is a pretty straightforward means of broadcasting information, and we’re pretty familiar with radio for audio recordings. (Your cars almost certainly still have radios in them, even if you plug them directly into an mp3 player instead.) Radio is pretty easy to set up, as you just need to have an antenna and a transmitter. Even more helpfully, the atmosphere doesn’t block radio waves, so you don’t have to worry about the air absorbing the signal you’d like to send out. This also means that the atmosphere won’t get in the way of shooting a signal up into space from the ground.

In fact, radio waves are so straightforward that this is also how we communicate with most of our artificial satellites. We use a very narrow range of the available radio frequencies for the kinds of radio stations that your cars are sensitive to, but there’s a lot of other frequencies that we can use for other things. And, as is our way, we have used these other radio frequencies for other things. A GPS satellite, for instance, uses the radio to communicate with the ground. These satellites use a frequency range called “L band”, which ranges from 1GHz to 2GHz, which in turn works out to wavelengths of tens of centimeters and longer.

JAXA astronaut Kimiya Yui captured this photograph from the Japanese Experiment Module (JEM) window on the International Space Station on Dec. 6, 2015. JEM, also called Kibo – which means “hope” in Japanese – is Japan’s first human space facility and enhances the unique research capabilities of the International Space Station. Image credit: NASA/JAXA

JAXA astronaut Kimiya Yui captured this photograph from the Japanese Experiment Module (JEM) window on the International Space Station on Dec. 6, 2015. JEM, also called Kibo – which means “hope” in Japanese – is Japan’s first human space facility and enhances the unique research capabilities of the International Space Station. Image credit: NASA/JAXA

Going from a GPS ping to sending data along the radio wave is relatively straightforward – and if you’ve got a data plan on your cell phone, you’re already doing it. The LTE network in the US is also roughly an L-band connection between cell phone and tower. The L-band is also of interest to astronomers, as it illuminates neutral hydrogen gas in nearby galaxies. This overlap in frequencies is one reason you’re not allowed to bring your cell phone near a telescope which is trying to observe in the L-band; you’d interfere with someone’s science data.

The radio connection to the ISS isn’t L-band, it’s Ku band (12-18 GHz) and S band (2-4 GHz), but the principle is the same. We can beam a signal up to the ISS, which has an antenna which lets them receive it, and then their computers can download an email. To be more precise, typically we beam a signal up to a satellite and the satellite slings it over in the direction of the space station. However, there are limitations to how fast your radio-based connection can communicate, and one of the issues is distance from the source. When you’re beaming a signal to space, and power drops with distance, the rate at which you can communicate also drops. Unsurprisingly then, by all accounts the internet on the International Space Station is pretty slow. Astronauts rate it “worse than dial-up” but it’s at least there, and lets them write emails, post pictures on twitter, and call home to their families.

Interestingly, Twitter only became a part of ISS life in 2010! Before 2010, the access to the internet was pretty limited, so if an astronaut wanted to put something up online they would have to email it to the ground team via their radio connection, and the ground team could log into their account on their behalf and post it for them. Considering that the ISS has been going since 1998, this is a relatively recent upgrade.

There is another potential upgrade to the internet in space being tested. The machinery for it was delivered by one of the SpaceX capsules in April, 2014, called OPALS. Opals stands for Optical PAyload for Lasercomm Science, and it’s successfully gotten data down from the ISS to a listening station in California. OPALS is cool because it uses lasers, which means we’re switching from an analogue radio signal to an optical one. As anyone who happens to have fiber optic cables for their internet can tell you, optical data rates are way better than the alternative.

Artist’s illustration of OPALS instrument firing a laser. Image credit: NASA/JPL

Artist’s illustration of OPALS instrument firing a laser. Image credit: NASA/JPL

If we get the ISS switched over to OPALS completely, the internet for the astronauts will speed up by a considerable amount – the OPALS team estimates it’ll be somewhere between 10 and 1,000 times faster than what they have now. Unfortunately the tech is still in the testing phase, so the internet won’t have a speed bump just yet. In order to really scale this up, you’d need to have listening stations all over the planet, and the laser itself will have to very accurately point itself at the listening station. When you’re moving as fast as the ISS is, pointing in the right direction is no mean feat. In fact, the ISS is moving so fast, there’s only about a minute and forty seconds of communication between the ISS and the current listening station before the space station goes over the horizon again.

If this optical technology can be fully implemented, the ISS will enjoy the internet at significantly higher speeds through the wonders of laser beams!  In the meantime, the ISS, along with a number of other uncrewed spacecraft, will continue to talk, video, send data, and tweet with the earth via radio signals, beamed down to us through a constellation of satellites.

 

Have your own question? Feel free to ask! Or submit your questions via the sidebar, Facebook, twitter, or Google+.

Sign up for the mailing list for updates & news straight to your inbox!

Could you see a spaceship in orbit by day?

Could you see a spaceship or station in orbit by day, if it were the size of an aircraft carrier?

In order to figure this out, we need to know the size of an aircraft carrier, how much light it would reflect, and have something to compare it to.

Going in order - the largest aircraft carrier I can find is technically a supercarrier, and measures 77 meters wide by 333 meters long. This gives us a reflecting area of 25641 square meters (2.56 square kilometers - this thing is massive).

In order to know how much light it would reflect, we have to know what it would be made of - on earth a lot of our marine craft are made of steel, which reflects 58% of the visible light that hits it. However, spacecraft don’t need to follow ocean rules exactly, so I’ve also considered the amount of light reflected off of aluminum, which is one of the most reflective metals out there; it reflects 91% of the light that hits it.

So, now to compare to something concrete. Fortunately, we have a space station to compare to - the International Space Station. The ISS is 72 meters wide and 108 meters across, which gives it a total surface area of roughly 7776 square meters, or 0.7 square kilometers. Comparing this to the surface area of the supercarrier, we find that the supercarrier is 3.3 times larger in reflecting area.

However, this doesn’t mean that the supercarrier is automatically 3.3 times brighter, since we haven’t taken into account how much light the ISS reflects relative to how much our supercarrier reflects. The ISS is designed to reflect as much light as possible, in order to try and best insulate the space station. The space station, on average, reflects about 90% of the visible light that hits it - the solar panels are slightly less reflective than the main body of the station, since they’re trying to absorb sunlight to power the station.

We’re going to want to compare the brightness of the ISS to the brightness of an object made of a different material, so we need to scale the brightness of the ISS by the fraction of light that’s reflected off of steel and aluminum. Aluminum reflects 91% of the light that hits it - the ISS reflects 90%: supercarrier divided by ISS will give us how much brighter (or fainter) aluminum is when compared to what the ISS is made of. These numbers are almost the same, so we should expect this factor to be almost exactly one, and it is: 1.01. Steel reflects much less light than aluminum, so we find that a steel space station would be only 64% as reflective as the ISS.

Now we can scale the brightness of the ISS by both reflectivity and size - for steel, we find that an object 3.3 times larger, but 64% as reflective gives us an object that reflects 2.12 times the amount of light that the ISS does. For an aluminum spacecraft, it would reflect 3.36 times the amount of light that the ISS reflects.

What does this mean in terms of visibility? A spacecraft the size of a supercarrier would be easily visible at night - it’s between 4.8 times (steel) and 7.7 times (aluminum) as bright as Venus. It would appear as an extremely bright star moving relatively quickly through the night sky. It’s also above the visibility threshold for daytime viewing. You can see Venus in the day if you know where to look, and since the supercarrier would be at least four times as bright as Venus, you should be able to spot the space craft during the day as well. However, it’s nowhere near as bright as the sun or the moon, so it wouldn’t necessarily stand out if you weren’t already looking for it.

Something here unclear? Have your own question? Feel free to ask! Or submit your questions through the sidebar, Facebook, twitter, or Google+.