Category Archives: Zulu

Amateur hour with Zulu time–Part 4


This post only means to show some of the “weirdness” some government agencies go through as they run their programs.  It is not meant besmirch any reputation of any agency or person.  Anyone who doesn’t take any of this with the grain of salt it deserves, maybe should think seriously about yoga.  But just so you understand, agencies are bureaucracies with masochistic cultures, so things can just get a little or a lot wonky—enough to stymie the smartest of engineers.  If you’ve ever seen the movie, “Brazil,” you kind of get an idea of how bad and weird things can be.  Sometimes there’s so much head-shaking going on in these agencies, you’d think you were one of those bobbing dolls sitting on a Volkswagen Van dashboard with blown suspension going down an extremely bumpy road.

In these past posts, I hope I’ve shown you there were good reasons for the adoption of Zulu time.  You know the British paid a hefty amount to John Harrison to develop a clock so British navies and merchants wouldn’t get lost at sea.  You know the establishment of the Prime Meridian is a key part of the longitude answer the British eventually came up with.  And you know Greenwich Mean Time’s establishment as the “Zero” reference time was just as important for navigation.  So much so, both Prime Meridian and GMT were accepted as standards internationally, too.  The fact the US military trains with Zulu time emphasizes the standard—so much so, it’s not even questioned.  It becomes a small thing, a rule and standard you don’t expect to disappear—until it does.

Umm, yeaahhh, we’re using a different time…

The standard was changed on me when I started working for an agency responsible for defending the USA against rogue missiles.  The weirdness started when I noticed other times than GMT (although GMT was also there) were being used for conducting test projects.  I had been out of the United States Air Force (USAF) a short time, but this time displacement felt like I had been moved to a different dimension.  The USAF used Zulu time for everything.  It didn’t mean people weren’t aware of local time, but for an organization conducting operations on a global scale, Zulu made sense.  Besides, the military had the ATP-1 (Allied Tactical Publication-1, Volume II: Allied Maritime Signal and Maneuvering Book) to abide by, too.  Soooo, this “Missile Defense” agency I worked for, led by a general, populated with a mix of military, retired military, analysts, engineers, etc., somehow figured Huntsville Time would be a great reference time zone.

I’m not kidding—there’s no such thing as “Huntsville Time.”  I know that.  There’s Central Time, which is the zone in which Huntsville, Alabama is located.  I must say, I’ve never had the privilege of attending Alabama schools, so maybe there is something extra special in the state’s school curriculum I wasn’t privy to. Madison County, in which Huntsville resides, is reputed to have the best schools in Alabama’s education system.  But that’s kind of like saying you have the smartest child of all the remedial kids.  Depending on your upbringing, some of this lore will not come as a surprise, to you, dear reader.  So we somehow had a Huntsville Time zone to deal with during missile tests.

Sometimes, if the missile tests spanned other time zones, things got mixed up.  Sometimes tests would include Hawaii.  So there was the Hawaiian Standard Time and others.  That particular time zone starts with “H” too, which really didn’t help.  But since I worked with satellites in the agency, our organization was using Zulu.  It almost seemed like I had been dropped in the middle of amateur hour during an ironic comedy.

Compensating for others’ incompetence

I eventually asked questions:  “Why aren’t we using Zulu or UTC as the only reference time?  We have tests and people all over the globe, why not coordinate both using Zulu?  People will confuse the times if you show all time zones in the countdown checklist.”  The answer I received was surprising and disheartening:  “Well, we’ve had a few people, including mission managers (one of the key test coordinators), show up late because they couldn’t figure out what time to show up.”   !!!!  I asked if we could, please, since our space systems were using Zulu, have only Zulu time on the test execution checklist.  I was given a “no” as an answer.  And honestly, I wasn’t inclined to repeat the request, because our teams were just so busy getting ready for tests.  Like in many organizations, the capable people were overtasked with many different things.

At risk of sounding like an old fogey, if anyone had showed up late because they couldn’t tell the time in the USAF, well, there would be a talk.  And maybe some drills on how to tell time.  If it happened again, then that person was obviously an ill fit for the required work and might be encouraged to seek out a different career.  But this agency, full of smart people trying to develop nation-saving tech, was unable to use only Zulu for its operations and unwilling to allow people to grow up and learn how to use it.  Mind you, this is only the same Zulu that most of the rest of the Western world uses for critical operations.

No drama…yet!

Fortunately, these problems and weirdnesses do get ironed out—but they never disappear.  And with each new test, someone will inevitably confuse HST with HSV or CST, but the test teams do catch them.  If they only used the one time, Zulu, it would be one less thing to worry about.  If they continue down the road of listing all the times of the different time zones involved, there will eventually be a mistake which the test team won’t be able to recover from.  This is a thing that never should be an issue to begin with.

So, as I stated right at the beginning of these posts, it’s a small thing, something you expect to be present and correct.  I definitely expected the “professional” civilian agencies to use the right time standard, in this case, Zulu Time.  If only because there’s a lot of history behind Zulu time, and a lot of good reasons to keep using it—at least until something better comes along.


World Time Z–Zulu Time, that is–Part 3

Z Clock

Zulu time is Z-time.  It’s really that simple.  It means zero hours, describing the offset of time from the Greenwich Mean Time longitude line.  Why Zulu and not Zero or Z?  It has to do with the alphabet and clear communications.  It has to do with the International Civil Aviation Organization’s (ICAO) needs and that need was clarity in critical communications.

In order to minimize mistakes in communications, the ICAO developed the phonetic alphabet.  If you’re an English speaker, you’re familiar with the basics of this alphabet.  All you have to do is say the letters a little bit differently.  So instead of pronouncing a letter like “S” as just “ess,” you’d verbally relay it as “Sierra.”  “F” would be relayed as “Foxtrot,” and of course “Z” would be “Zulu.”  Mystery solved!!

Such an alphabet made communications easier in international settings to enhance communications for cooperation, so groups like the North Atlantic Treaty Organization (NATO) adopted the ICAO phonetic alphabet.  In fact, NATO developed a publication, the Allied Tactical Publication (ATP)-1, Volume II: Allied Maritime Signal and Maneuvering Book, which lists the phonetic alphabet and explains how to use it.  There are even pronunciation guides for the phonetic alphabet, since not everyone using it is a native English speaker.  Especially those people living in the southern states.

The US military is a part of NATO, so little wonder the military services in the United States use the phonetic alphabet to this day.  It’s not that local time isn’t used by the military services for day to day for things like meetings, lunch, and physical training.  Local time is always there, but when it comes to missions, Zulu time is the expectation, not the exception.  Zulu time could mean the difference between life and death when the military is conducting operations.  If each service used a different standard of time while conducting cooperative operations, things would get very interesting indeed.

The global nature of satellites has promoted the use of Zulu time in space operations and not just in the military space operations.  Whether commercial, government, or military, it doesn’t make sense for satellites to reflect whatever local time zone they may be flying over.  The satellites fly over the time zones too quickly (within minutes for some satellites—and yes, I know geosynchronous satellites are pretty much over the same spot on the earth).   Ground stations for satellites also use Zulu as a common time reference, no matter if they’re located in Antarctica, Guam, or Virginia.  Using Zulu helps to keep things simple.  And that may be the best reason to use Zulu time.

So, as learned from the previous two Zulu posts, we have two common, universally accepted reference points.  The Prime Meridian, is still, more or less, the accepted longitude reference, even for satellites (the International Earth Rotation and Reference Systems Service most recently puts it about 102.5 meters east of the Royal Observatory in Greenwich).  And time is still based off of that longitude as Coordinated Universal Time (UTC) or Greenwich Mean Time (GMT).  Plus, now you know Zulu time is pretty much synonymous with UTC and GMT, as well as Zulu time zone’s relationship to space operations.

From mariners to space operators, ships to satellites, Zulu time has been a standard for knowing where things are, coordinating actions, and keeping things simple.  It’s just such a pervasive, useful, small-seeming thing.  Which leads to the anecdote I’ve been wanting to tell you.

Dropped balls, accurate time, Zulu, and space operations–Part 2

My inspiration to write this particular series of posts was the latest switch from Daylight Saving Time (DST).  There were the inevitable posts and soft news arguments and articles about the reasons for DST.  I’m not going to write about DST, but it all reminded me of an experience with a certain defense agency—one that defends against missiles—and the importance of Zulu time.  We will get to that anecdote once I’ve finished providing an understanding of the historic actions and eventual reasons of why Zulu time was established and how that relates to space operations.

In my last Zulu time post I wrote the British government offered 20,000 pounds to the first inventor who developed “a method for determining the longitude within 56 kilometers.”*  Believe it or not, it took a long time for someone to get it right:  nearly 45 years!!

The inventor, John Harrison, developed the H4 marine chronometer in 1759—the world’s first truly accurate timepiece.  The H4 exceeded specifications:  it could help determine the longitude within 1 kilometer (time-wise, this meant it was off by ONLY five seconds)!!  Sure, in this world of ultra-precise Global Positioning Satellites (GPS) such an error would be very problematic.  But in 1759, there was no such thing as GPS.  For more about the H4 marine chronometer, read the wiki and the excellent references it recommends.

How does a timepiece help with determining location?  There are many great resources, but start with the Royal Observatory’s “Longitude Problem” post.  Summary:  Every 15 degrees of longitude east or west of the Prime Meridian represents one hour forwards or back from the Greenwich time (so, 30 degrees=2 hours, 75=5, etc.).  A very accurate clock, like H4, synchronized to a fixed location’s time (Greenwich Mean Time), and a navigator’s sun observations to determine the ship’s distance from that fixed location, would render a precise (for those days) ship location.  As an aside, navigators were also in aircraft, like the F-4 fighter jet, for the same reasons.

Harrison’s technology was so good, so robust, the H4’s internal design was the basis of for timepieces well into the 20th century.  You can still go see the H4 in the National Maritime Museum, Greenwich, Britain.

Interestingly enough, Greenwich is also where another important activity occurred:  the dropping of a “time ball.”  Every day at 1 PM, since 1833, the Greenwich Observatory (pictured below), drops a ball to allow nearby marine vessels to synchronize their timepieces, their marine chronometers, to retain relative time accuracy (the ball is the red sphere on top of the tower in the picture).  Since Britain was an empire then, with a lot of commerce going on between continents, there were a lot of ships dependent on the punctual actions of the Greenwich Observatory (read this wiki if you’re interested in how the observatory kept time).  The punctuality and accuracy of the time ball drop created favorable circumstances for the eventual adoption of the Greenwich Mean Time as the international reference standard in 1884 AD (and the Greenwich longitude as the accepted Prime Meridian).

Royal Observatory, Greenwich Image by ChrisO

The United States also used time balls to help mariners keep accurate time.  In today’s terms, we call that action a clock hack or time hack.  Time balls were used by sailors until about the 1920’s, when radio time signals replaced their use.  Time hacks continued, with a bigger user pool relying on radio time signals to synchronize equipment, clocks and watches.  Radio time signals continue to be broadcasted.  If you’ve ever dialed (303) 499-7111, you’ve already heard an example of what part of the radio time signal sounds like, courtesy of the United States National Institute of Technology and Standards (NIST) WWV radio station.

Or if you have the right radio receiver, you can try to listen for it on the channels listed on the web page.  However, since you’re probably  reading this on a computer, you always have the option of using NIST’s clock synchronization for your computer–just go to their “Internet Time Service” page to find out how.  There are so many options for you to find out the accurate time–and to think nearly a hundred years ago, this technology was all still being tested.

Of course, something much better, much more accurate came along:  Global Positioning Satellites.  Also, we haven’t really talked about Zulu time itself—but next post we will.  And, I haven’t forgotten about that anecdote.

*Citation:  Graham-Cumming, John, The Geek Atlas:  128 Places Where Science & Technology Come Alive, O Reilly, 2009, Chapter 049, page 185.

Battleship, space operations, and Zulu–Part 1

Blue Stop Sign

Sometimes it’s the small things, the things a person takes for granted, that get a person out of sorts if not in place or wrong.  Ever heard of a blue stop sign?  No, and there’s probably a good reason for it, which will not be explored here.  But think of the confusion a blue stop sign might create.  It’s one of those very small, detailed conventions which we never give much thought to, but could really make a person’s day bad.  Time is also one of those things most of us take for granted.  But it’s not as small a thing.

Specifically, Zulu time.  For most of the rest of the world, the term more commonly used is Greenwich Mean Time (GMT) or Coordinated Universal Time (UTC).  But in the US military and other three-letter government agencies, the standard terminology is Zulu.  What do all three terms mean?  And what do they have to do with space operations?  Perhaps a short history lesson involving cartography, politics, military, and commerce is necessary for illumination.

A few hundred years ago, the British (yes, the same ones responsible for Mr. Bean and Red Dwarf) were very interested in giving their ship captains the ability to locate a ship’s position in the ocean with great accuracy.  After all, when a country is a naval and commercial power, knowing one’s precise location makes things simpler (it wasn’t unusual for some navies to get lost), so geographic coordinates were used.  This meant they needed two precise measurements, the latitude and the longitude.


The Battleship board of Earth

I will use the game, Battleship, to quickly illustrate.  Imagine the globe, flattened and in front of you like the Battleship board (if you can’t imagine it, use the picture above).  You remember the grid with letters across the top?  Those letters and the columns under them represent longitude.  And the numbers on the left hand column of the board?  Those, as well as the rows to the right of them, represent  latitude.  So when you’re attempting to sink an opponent’s ship, you would say something like “A,4!”  So you’re actually calling out the longitude and latitude of the area you’re targeting, hoping to sink a ship.  The letter and number together become a geographic coordinate (a cartographic crosshair).  Normally, real-world geographic coordinates are all numbers, stated with latitude first, then longitude—and they are more precise than what’s used in Battleship.  There are many great sites and explanations of the all these:  geographic coordinates, latitude and longitude.  Go to them if you really want to get into the details.

What I recommend is for you, dear reader, to just try to understand there was a need for a common reference point for British ships to navigate the oceans accurately.  This reference point, called a Prime Meridian, ended up as the longitude line running through the Royal Observatory in Greenwich, England, from North to South Pole.  This means that Greenwich’s longitudinal coordinate is 0 degrees.  If you go west, it can go as high as +180 degrees.  If you go east, you get to -180 degrees.  The Prime Meridian was so important, other countries, such as France, the Netherlands, Belgium, Spain, Portugal, and more, had their own Prime Meridians—some for longer time periods than others.  So, what do all of these meridians have to do with time?

Establishing the Prime Meridian is just part of determining the longitude and a ship’s location accurately.  The other part was time, and inventing the necessary technology (and terms) to know time accurately.  Accurate time was so important to the British government that, in 1714 AD, they offered a bounty of 20,000 British pounds to the first inventor who could “develop a method for determining the longitude within 56 kilometers.”*  And that wasn’t as easy as it sounds…more about that tomorrow.

*Citation:  Graham-Cumming, John, The Geek Atlas:  128 Places Where Science & Technology Come Alive, O Reilly, 2009, Chapter 049, page 185.