Satellites and Orbits – Background and Context

It was no lesser mind than the 17th Century super-genius Sir Isaac Newton who first suggested the possibility of a man-made object launched into orbit around the Earth.  I.E. a satellite.

It took 300 years to see that vision become a reality.  And to date, there have been around 6,600 satellite launches, with approximately 3,600 satellites still in orbit.  Of these only 1,071, or so, are fully functioning.

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A Modern Telecommunications Satellite

Words like Low Earth Orbit and Geo Stationary Orbit are common expressions in the satellite and telecommunications communities.  But what do they really mean?

Geosynchronous Orbit

This is where the period of rotation is not 24hrs but some multiple (or fraction) of 24hrs.

Such a satellite would pass over the same spot on the Earth at a given time (or times) each day.  For example, a satellite in Equatorial Orbit with a period of rotation of 12hrs, would pass over the same spot twice each day.

Geostationary Orbit

Geostationary is a special case of “Geosynchronous orbit”.

In the 1940’s Arthur C Clarke, published an article in Wireless World.  Clarke explained that a satellite orbiting the Earth at an altitude of 36,000 km above the equator would circle the Earth in exactly 24Hrs.  Such a satellite would maintain a “geostationary position”.  Thus, to observers on Earth, it would appear to remain motionless in the sky.

Of our 1071 satellites still functioning approximately 500 are in “Geostationary” or “Geosynchronous” orbit.  I.E.  around 36,000 km above our heads.

Medium Earth Orbits (MEO)

These are satellites orbiting at an altitude of between 10,000km and 20,000km.  This distance places them between the Van Allen belts where radiation exposure is minimized.  MEO’s are not necessarily  limited circular orbits.  We have approximately 50 satellites in MEO.

Low Earth Orbits (LEO)

Satellites such as the International Space Station (ISS), are in LEO.  Typically, such orbits are 1000km or less and circular.  This facilitates easy “re-visit” capability.

Low Earth Orbiting satellites have a relatively short period of rotation, usually of the order of 100 minutes or so.  This means that they speed across the sky and disappear below the horizon quiet quickly.  As such until recently they were thought inappropriate for Telecommunications.  However, during the 1990’s a “constellation” of these satellites was deployed making them useful for telecommunications.  (Eg: Iridium Satellite Constellation).  There are approximately 500 satellites screaming across our sky in Low Earth Orbit at present.

And more recently Sir Richard Branson’s Virgin Galactic are investing heavily into Satellite Internet technologies, such as Halo-Fi.

Newton would be very proud……..

Have you ever seen a satellite with you naked eye? 

And what of the future of satellite technology?  Have you heard of the amazing new Cubsat Technology?

Why Grandma budgeted with money in jars?

As promised, I’m back with the second installment of my thoughts on exponential behaviour.

My Grandmother had money in jars for everything…. Rent, food, housekeeping, buttons, even pin money…  everything!

You may recall my last blog outlining the relationship between exponential numbers, science and finance.  (This has always been a fascination of mine – I mean, interest rates and satellite orbits?? Why?)

Well “e” (or 2.71828…) is a very unique number….

We’ll get to that in a minute.  Let’s examine natural phenomena –  Bacterial growth rates.

Binary Fission
Bacteria reproduce by “binary fission”

Let’s assume a single bacterium is put in a jar at 11pm.   The bacterium reproduces itself every minute, i.e. the number of bacteria in the jar doubles every minute.  The number of bacteria increases in the sequence 1,2,4,8, etc.   After 1 hour the jar is completely full….

I ask you at what minute is the jar half full?

That’s right –  at 11:59 pm

And at 11:58 pm it is a quarter full.

And at the 11:57 pm it is an eighth full.

And so on, right back to the original bacterium.

Why is this important?

Well, interest rates work that way too!  We all know that your money is unlikely to double every minute, but it will double.  For example, at 10% your money will double every seven years.  And this is easy to calculate…. Just divide 70 by your interest rate:

70/10 = 7 years

The math is based on the natural logarithm of 2 (ie doubling), and 100Ln 2 = 69. Whatever, use your calculator…  but trust me its close enough to 70.

Another question…

At 11:58 pm, how many bacteria would have realized that they were running out of room?

And if you retire at age 65 and your money is invested at 10%, how old are you at 11:58pm?

Yep, that’s right….  You are 51 years old.

Have you got enough money in your jar?

e” – where Finance meets Science

Many of you would know I am  a trained accountant.  Most would not know that my original training was in science and engineering.  It’s that aspect of my life the I would like to write about now.

All of you would however be familiar with the concept of interest rates.  A nightly topic on the news, interest rates determine how much spare cash we have after the mortgage payment.  And the total mortgage paid is a simple calculation.  To save time, I’m going to skip the math…  but the formula is:

FV = PV(1+r)^t

Where:

FV = Future value

PV = Present Value

r  =  Interest Rate

t  = time

its the formula for calculating the total amount you pay – and, (just like me), its not very sexy!

The Cool Thing though, is if you have a greedy banker!!

Continue reading

Whatever your problem, its likely graphene can fix it.

(Or how to win a Nobel Prize using only sticky-tape).

Graphene is a form of Carbon and is derived from graphite.  Scientist have long suspected that Graphene possessed amazing qualities.  And although they knew that graphite consisted of stacks of “graphene sheets”,  most thought it impossible to retrieve a single sheet.

That was until two physicists at Manchester University began playing with sticky-tape and graphite.  In 2004 Andre Geim and Konstantin Novoselov simply adhered sticky-tape to a block of graphite and removed it.  What they discovered was amazing.  And they won a Nobel prize for their efforts.

Graphene, carbon and sticky tape

Micro-flakes of graphene.  Incredibly thin with the Carbon atoms arranged in a perfect honeycomb pattern.

Fun Facts about Graphene

  1. One sheet of Graphene is just one atom thick.  A sheet the size of a football field would weigh less than a gram.
  2. Graphene is 200 times stronger than steel and harder than diamond.
  3. It would take three million sheets to make a stack 1mm high.
  4. A sheet one atom thick is sturdy enough to be picked up
  5. It conducts electricity better than copper or silicon.

It can be bent, folded or rolled.  It is so strong that Colombia University estimates it would take a pressure equivalent to an elephant balanced on a pencil to break through a layer of graphene as thick as plastic food rap.

Graphene

The possible applications are mind boggling.  Aircraft parts, flexible mobile phones, smaller and faster computer chips, desalination filters, biofuels and powerful long-life batteries that can be charged very quickly.

It is even suggested that graphene could be used to regenerate nerves in damaged limbs.

It seems whatever the problem, the solution is Graphene Baby!

What problems might it solve for you?

 

 

 

 

 

 

 

 

 

 

 

 

This is sooo cool.   A total solar eclipse is due on the 8th of march.  The moon will pass in front of the Sun at 6pm AEST and a total eclipse will move north east through Indonesia, Papua New Guinea and Borneo.

At its widest the shadow will be 156Km wide and total darkness will last between 90 seconds and 4 minutes.  (Plenty of time to cast your sacrificial virgin into the volcano!!)

Parts of Northern Australia will experience a partial eclipse.  However you can experience the event Live via the following link.  View Eclipse Live.

Also Solar Dynamics will post live images as the event takes place.   Solar Dynamics  is a really cool NASA site and I suggest you check it out anyway.

 

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