Tag Archives: Geosynchronous

NASA Space Place – The “G” In GOES Is What Makes It Go

Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. NASA Space Place has been providing general audience articles for quite some time that are freely available for download and republishing. Your tax dollars help promote science! The following article was provided for reprinting in May, 2015.

By Dr. Ethan Siegel

2013february2_spaceplaceGoing up into space is the best way to view the universe, eliminating all the distortionary effects of weather, clouds, temperature variations and the atmosphere’s airflow all in one swoop. It’s also the best way, so long as you’re up at high enough altitudes, to view an entire 50 percent of Earth all at once. And if you place your observatory at just the right location, you can observe the same hemisphere of Earth continuously, tracking the changes and behavior of our atmosphere for many years.

The trick, believe it or not, was worked out by Kepler some 400 years ago! The same scientist who discovered that planets orbit the sun in ellipses also figured out the relationship between how distant an object needs to be from a much more massive one in order to have a certain orbital period. All you need to know is the period and distance of one satellite for any given body, and you can figure out the necessary distance to have any desired period. Luckily for us, planet Earth has a natural satellite—the moon—and just from that information, we can figure out how distant an artificial satellite would need to be to have an orbital period that exactly matches the length of a day and the rotational speed of Earth. For our world, that means an orbital distance of 42,164 km (26,199 miles) from Earth’s center, or 35,786 km (22,236 miles) above mean sea level.

We call that orbit geosynchronous or geostationary, meaning that a satellite at that distance always remains above the exact same location on our world. Other effects—like solar wind, radiation pressure and the moon—require onboard thrusters to maintain the satellite’s precisely desired position above any given point on Earth’s surface. While geostationary satellites have been in use since 1963, it was only in 1974 that the Synchronous Meteorological Satellite (SMS) program began to monitor Earth’s weather with them, growing into the Geostationary Operational Environmental Satellite (GOES) program the next year. For 40 years now, GOES satellites have monitored the Earth’s weather continuously, with a total of 16 satellites having been launched as part of the program. To the delight of NASA (and Ghostbusters) fans everywhere, GOES-R series will launch in 2016, with thrice the spectral information, four times the spatial resolution and five times the coverage speed of its predecessors, with many other improved capabilities. Yet it’s the simplicity of gravity and the geostationary “G” in GOES that gives us the power to observe our hemisphere all at once, continuously, and for as long as we like!

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

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Caption: National Oceanic and Atmospheric Administration, of the first image ever obtained from a GOES satellite. This image was taken from over 22,000 miles (35,000 km) above the Earth’s surface on October 25, 1975.

About NASA Space Place

The goal of the NASA Space Place is “to inform, inspire, and involve children in the excitement of science, technology, and space exploration.” More information is available at their website: http://spaceplace.nasa.gov/

Asteroid 2012 DA14 (& Little Hope For CNY (Viewing))

Greetings fellow astrophiles!

I begin with a little bit of history from the NASA Voyager website: voyager.jpl.nasa.gov

The Voyager delivery accuracy at Neptune of 100 km (62 mi), divided by the trip distance or arc length traveled of 7,128,603,456 km (4,429,508,700 mi), is equivalent to the feat of sinking a 3630 km (2260 mi) golf putt, assuming that the golfer can make a few illegal fine adjustments while the ball is rolling across this incredibly long green.

I include this piece of historical content to put into context any discussion about a 2012 DA14 impact (which, at this point, falls clearly into the conspiracy theory regime). The world has a very good handle on Newtonian Mechanics and, when it is reported by NASA physicists that something is going to miss the planet by 27,000 km (OK, fine. 27,000 km from the Earth’s center. As the point on the Earth’s surface farthest from the Earth’s center is 6,384 km away, DA14 will miss by “only” 20,616 km), you can believe it. If we can be off by 100 km after 12 YEARS in space, be assured we can be within that same 100 km with a year’s worth of data collection.

With the good news out of the way…

As the newest reports about 2012 DA14’s path make clear, its passing within geosynchronous orbit will be a treat for observers in Indonesia and an otherwise great view for Europe, Asia, and Africa. And by great, I mean that the predicted apparent magnitude will not reach smaller than 7.4 (smaller = brighter. Naked Eye viewing trails off rapidly after magnitude 4, making 2012 DA14 a “big binocular” object even at its closest approach. The Sun, on the other hand, is at magnitude –26.74 from Earth), so it will be great with the aid of optics. CNY, and the Americas in general, will only be able to observe 2012 DA14 on its “way out,” after closest approach. As it will be moving at quite a clip away from us, it will be quite a difficult object in CNY to find for anyone outside on the night of the 15th. Reports seems to indicate it will be at magnitude 11 by the time the East Coast could see it, which is a heroic magnitude for most any amateur telescope).

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CAPTION: Path of 2012 DA14 (in Universal Time (UT) and as viewed from the Earth’s Center) on February 15/16. Click for a full-sized version. From www.virtualtelescope.eu.

And, if you’re still freaked out about impact, note that we (CNY) will STILL be on the wrong piece of Terran real estate. That said, its trajectory is even wrong for colliding with geosynchronous satellites, so your cell phone service won’t be impacted, either.

I am pleased to report that the best 4 minute discussion of 2012 DA14 has been put together by an organization I’ve been a member of for over 15 years – The Planetary Society (co-founded by Carl Sagan, currently CEO’ed over by Bill Nye, the list of activities in space science and public outreach is considerable). Bruce Bett’s youtube video is provided below. If Snow Storm Nemo has anything to say about it, you’ll have plenty of time this weekend to watch and take notes.

CAPTION: Planetary Society Director of Projects Bruce Betts reassures us in this brief and fascinating explanation of what will happen–and what WON’T happen–when this big asteroid comes closer to Earth than many satellites.

You can read a full article about 2012 DA14 at the Planetary Society website: www.planetary.org/explore/projects/neo-grants/2012da14.html. A thorough FAQ can be found at www.planetary.org/explore/projects/neo-grants/2012-da14-faq.html.