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What is a uSv?

It’s a micro-Sievert. Micro means one millionth. It’s abbreviated the Greek letter “mu”, which I don’t have on my keyboard, so I use a “u” which is sort of close.

A Sievert is a unit of radiation that has to do with the absorption rate of radiation in human flesh. Some guy with the last name Sievert named it.

I talk about it more at the bottom of the page in my first couple of posts.

On the ground in Aspen

This is the first opportunity that I’ve had to get a radiation reading on the ground, in the mountains. I had heard that the levels were elevated in places, such as Denver, where you’re quite a bit above sea level. For a comparison, let me show you the levels of radiation at various cities around the US.

Raleigh, NC – .11 uSv/hr
Tampa, FL – .10 uSv/hr
Dallas, TX – .07 uSv/hr
Los Angeles, CA – .13 uSV/hr
Phoenix, AZ – .11 uSv/hr

At 8500 feet above sea level, here in Aspen:


I would have guessed the level to be higher. So this is definitely a number I could live with if I were to spend my whole life up here (I wish!).



New job, new data

Hello all! Some of you may have been wondering where I went to. I haven’t posted anything for quite some time. Well, without an airplane to fly, it became hard to get high altitude data!

So I got a new job in a new plane in a new place. I’m flying the Hawker 800xp now from a base in Tampa, FL. This aircraft can fly at 41,000′ so the data I collect should be good to go!Hawker

I just flew a trip from Tampa to Boston and thought I’d let you know that NOTHING HAS CHANGED in the upper atmosphere.  This trip was flown at 39,000 feet.  Other than forgetting to turn off the detector after we landed, the graph looked pretty boring.  Here it is…


Radiation in Space

Many people have asked me what the dangerous radiation levels are.  The answer that I’ve found is 100,000uSv in a year.  Cancer has been directly linked to this exposure value.  Jet pilots and Flight Attendants can expect to get around 6000uSv per year if they fly 800 hours.  That’s not to say radiation can’t make you sick at lower levels.  It can.  But it’s really hard to link things like the common cold to a couple days of flying at high altitude.  This is what has caused so much confusion about it and why it’s so hard to find concrete data on what radiation can do.  The best advice I can give to aircrew and frequent flyers is to maintain a healthy lifestyle.  Any detrimental affects to the mild doses we receive are probably magnified by poor eating and other health habits.

So what’s the radiation level at the International Space Station?

I’ve been getting measurements at a maximum altitude of 8.5 miles.  The International Space Station orbits at about 280 miles up.  The average astronaut on the ISS, during their 6 month stay, gets a whopping 70,000 uSv!  So you can see why they don’t, normally do more than 6 months.

In fact, man will never conquer space travel without handling the radiation problem.  Low Earth Orbit is about the best we can do for extended periods of time, right now.  The Van Allen belts extend from roughly 600 miles to 22,000 miles above the Earth.  These are belts of high levels of radiation that men can’t stay in for long.  Above this, the effects of the Earth’s magnetosphere are so diminished, that solar activity is uninhibited.

Throughout the years of the Apollo moon landings, there were regular solar flares.  A couple of them would have cooked the astronauts going to the moon.  The success of these missions was mostly luck of timing.  The future of space travel depends entirely on finding the best ways to shield against radiation.


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Northbound to Germany

Here is data from a quick trip from Saudi Arabia to Germany.


Flying Near The Equator

Maldives radiation-resized

Whew, I just did 4 round trips between Saudi Arabia and the Maldives.  That was 40 hours of flying in one week!

Maldives route-resized

The Maldives are a group of islands (atolls actually) to the south of India.  The country of Maldives actually consists of over a hundred tiny islands.  It’s like no other place on Earth.  Every island has it’s own purpose.  When you land at the airport you’ll have to take a boat to your hotel on another island!  Yes, there is the airport island.  Next to it is the city island.  Between the two is the prison island. And, pretty much, all the rest are resort islands.  They get no hurricanes and the temperatures are decent throughout the year.  There are no dangerous animals.  There are nearly no bugs.  There’s always a warm breeze, but it’s rarely too strong.  The water is clear blue and there’s tons of exotic fish.  Parrot-type birds and giant bats live in the trees.  The place is a paradise of paradises.

Maldive islands-resized

Here’s me on the boat going to our resort hotel.Maldives boat-resized

Enjoying myself in the middle of January.  Sometimes I can’t believe I get paid for this!Maldive1-resized

We did a ton of flying.  A round trip in the G-IV was 10 hours.  Twice we flew all night with no sleep.  It’s been an intense and exhausting week.  But we finally had a full day off yesterday and I spent it snorkeling in the deep blue waters off of Paradise Island Resort.  Amongst all the tropical fish I saw 5 reef sharks.  It was spectacular!

Oh yes, what about the radiation?  I almost forgot.  I did have my meter on and recording during the flights.  So what did we learn?

Radiation levels in the air over the equator are relatively low!  Whereas the gamma radiation levels over the North Atlantic were over 4.0 micro-Seiverts per hour (uSv/hr) the levels near the equator were around 1.8 uSv/hr.  We consistently flew at 40,000′-43,000′ and there was little difference between altitudes.  These results were all between the latitudes of 4 and 22 degrees North.

Here are some graphs of the flights.  I have more, but they look about the same.

This one was southbound.

1 Riyadh to Maldives

This one was northbound.  It drops at the end because I forgot to turn the meter off after we landed.

2 Maldives to Riyadh

This one was southbound.

4 Riyadh to Maldives

It can clearly be seen that the radiation level at the southern end of the route (4 degrees north of the equator) was lower than at the northern end (22 degrees north).

I did discover something interesting, though.  The ground level radiation varied a lot more than it does on the ground at northern latitudes.  During the day, the gamma radiation was about .11 uSv/hr measured on the porch of my beach-front villa.  Every night, in the Maldives, it dropped down to about .06 uSv/hr.  As we are measuring with Gamma rays, primarily cosmic radiation, these results make sense.  At night the Earth is blocking the sun’s rays and the radiation level drops.  I have not seen this extreme variation at home (36 degrees north) or anywhere else.   The bulge of the Earth between the meter and the sun has a marked affect.

However, as you can see from the graphs above, the effect is not magnified in the upper atmosphere.  Day or night it’s about the same.  There’s a slight rise during the day, but only a little.  The affect is of little note compared to the giant rise in radiation levels from the change in altitude.

Tomorrow I’m flying to Berlin :-0


Radiation Drop


The north and south poles of the earth allow more cosmic radiation through because the earth’s magnetic field, at these points, is weaker.  The majority of electrified particles arriving at the earth, via the solar wind, are deflected around it by the magnetic field of the earth.  An electrified particle is called an ion and ions, obviously, have positive or negative charges.  Many of these ions are radioactive.  Some radioactive particles, such as free neutrons (technically called secondary neutrons), don’t have a charge.  These particles aren’t stopped by the earth’s magnetosphere, but are stopped by the earth’s atmosphere.  So we really have two things protecting us from cosmic radiation.  The magnetosphere and the atmosphere.  The poles are less protected by the magnetosphere and the upper altitudes are less protected from the atmosphere.  So then it follows that the closer you get to the equator, the less cosmic radiation there will be.  And we proved it with this flight.  As we flew south, the radiation dose rate looked like this:


At 41,000′ and 46 degrees north latitude, the dose rate was 3.2 uSv/hr

At 41,000′ and 22 degrees north latitude, the dose rate was 2.0 uSv/hr

It was nice to get to some warm air.  Eighty degree weather and a beachfront hotel awaited me in Jeddah, on the Red Sea.