Artificial Satellites

I recently read the biography, Elon Musk: Tesla, SpaceX, and the Quest for a Fantastic Future, by Ashlee Vance. (Is it wrong that I had a case of the Donna Changs and thought that Ashlee Vance was a woman; and that I was a little disappointed when I found out that she was a he?) It shouldn’t matter, I know, but I just kind of thought it would be interesting to get a female perspective on one such as Monsieur Musk. 

Regardless, the book was très bien and more to the point, it got me thinking about things I rarely ever think about, things like space travel and satellites. And having formerly known absolutely nil about rockets and satellites, they have since become the latest additions to my long list of fleeting obsessions.

That said, just watching the astronauts bounce around inside the International Space Station makes my chest tighten with claustrophobia, let alone the thought of being launched to space atop rockets. No thanks! Of the many things I know about myself with an absolute certainty, is the fact that if calamity was to strike our fair planet, in a manner warranting mass evacuation to space, I would be one of the last remaining souls left clinging to terra firma.

My personal phobias aside, I remain completely humbled and awestruck by the vastness, beauty and mystery of the Cosmos. The black canvass of Outer Space, wondrous in its expanse, cold and mysterious, and punctuated with flecks of twinkling lights, brilliant and dancing in the ocean of darkness.  

And I am relieved that there exist amongst us braver souls with better-wired brains than mine, so that the beauty and wonder and knowledge gleaned from their labors can be shared with those of us who have our heads tilted toward the skies whilst our feet remain planted firmly on the ground.

Artificial Satellites can be defined as bodies placed in orbit around the Earth or another planet in order to collect information or for communication. [1]

In a 1945 article in the magazine Wireless World, the English science fiction writer Sir Arthur C. Clarke described in detail the possible use of communications satellites for mass communication. [2]

Fast forward to October 4, 1957 and the world's first artificial satellite, the Sputnik 1, was successfully launched into orbit by the former Soviet Union. [3]

Sputnik 1's radio signal as heard on October 4, 1957:

Sputnik 2 was launched by the former Soviet Union on November 3, 1957 and carried the first living passenger in orbit, a stray dog named Laika. [4]

At the time, the technology did not exist to safely de-orbit and return to Earth.

Laika died within hours of take-off from stress and overheating. [4-5]

She was the first of 36 dogs sent to space by the Soviets prior to Yuri Gagarin becoming the first human to orbit the earth. [5]

On January 31, 1958, the United States successfully launched its first artificial satellite, the Explorer 1. [6][22]

As of October 2013 there were approximately 1071 operational satellites in orbit around the Earth. [7]

• With about half in Low-Earth Orbit, just a few hundred km's above the Earth's surface. Examples include: the International Space Station, the Hubble Space Telescope, and many Earth observation satellites. [7]

• The United States Space Surveillance Network (SSN) currently tracks more than 8,000 man-made orbiting objects (the majority of which are space debris). The rest have re-entered Earth's atmosphere and disintegrated, or survived re-entry. [8]

SATELLITE ANATOMY 

The Body:  The body, or bus of a satellite holds all the scientific equipment and other necessary components of the satellite. It serves to:

• protect from collisions with space debris; 
• protect from the sun’s radiation; 
• protect the satellite during exposure to temperatures ranging from 120 degrees below zero to 180 degrees above zero; [28] 
• conducts heat away from electronics; 
• provides structural support. [29]

The Payload:  A weather satellite would have a payload that consist of an image sensor, digital camera, telescope, and other thermal and weather sensing devices. [28]  A communications satellite would have a payload of transponders, antennas and switching systems to receive, amplify and re-transmit signals from and to Earth satellite transmission stations. [20]

Internal Computer: Logs every activity of the satellite, receives information from the ground station, and takes care of any general maintenance. (Telemetry, Tracking and Control (TT&C)) [29]

Grapple Fixture: Grapple fixtures have an electrical connector on the end of the pin which can join with an electrical adapter at the end of the Canadarm, allowing electrical power and data communications to move from the shuttle to the satellite when it is grappled. 

This is used to preserve a satellite's batteries during deploy and retrieval activities. [29] 

Attitude Control: Attitude determines which way the satellite’s cameras are facing, and the angle the satellite makes with the object it is orbiting. To stabilize a satellite, the satellite must have a system that keeps it moving evenly through its orbit whilst ensuring the solar panels remain constantly exposed to the sun. [29]

Control Electronics maintain communications with ground control stations which monitor the satellite's performance and control its functionality. [20][28]

The Communications System has a transmitter, a receiver, and various antennas to transmit data to the Earth.

The Power System needed to power and operate the satellite is usually an efficient solar panel array that obtains energy from the Sun’s rays, as well as batteries. [20]

TYPES OF SATELLITES 

Research Satellites measure fundamental properties of outer space, for example: magnetic fields, the flux of cosmic rays and micrometeorites, and properties of celestial objects. (Hubble Space Telescope, International Space Station) [28]

• NASA launched the Hubble Space Telescope in 1990. Hubble travels around Earth at about 5 miles per second. That is as fast as driving a car from the East Coast of the United States to the West Coast in 10 minutes. Hubble takes pictures of planets, stars and galaxies. It has seen galaxies that are trillions of miles away. [40]



Echo 1

The first communications satellite was Echo 1. Launched in 1960, it was a large metalized balloon that reflected radio signals striking it. [28]

This passive mode of operation quickly gave way to the active mode, in which complex electronic equipment aboard the satellite receives a signal from the earth, amplifies it, and transmits it to another point on the earth. [28]

Communications satellites provide a worldwide linkup of radio, internet, telephone, and television services. [20][28] Each service requires a different amount of bandwidth for transmission. [20] The bandwidth available from a satellite depends upon the number of transponders provided by the satellite. [20]

A network of 29 Intelsat satellites in geosynchronous orbit now provides instantaneous communications throughout the world. [28]

Meteorological satellites provide continuous information about large-scale atmospheric conditions. (Example: Geostationary Operational Environmental Satellites)

“Precipitation radars measure the radar echo from rainfall to determine the rainfall rate over the Earth's surface; and cloud profile radars measure the radar echo return from clouds to provide a three dimensional profile of cloud reflectivity over the Earth's surface.” [24]

The Navigation Satellite for Time and Ranging/Global Positioning Satellite System (Navstar/GPS) consists of some 24 satellites approximately 11,000 miles above the surface of the earth in six different orbital planes. [28]

Military satellites may be equipped with infrared sensors that track missile launches; electronic sensors that eavesdrop on classified conversations; and/or optical and other sensors that aid military surveillance. [28]

• Civilian applications for military satellites have included: satellite photographs showing surface features and structures in great detail, mapping, geology, agriculture, archaeology and marine surveillance, [27] as well as fire sensing in remote forested areas. [28]

Because a satellite in orbit cannot transmit information to Earth if it does not have a clear view of a ground station, Tracking and Data Relay Satellites (TDRS) are used to forward information from a satellite until it reaches the appropriate ground station. TDRS's provide near continuous communications with satellites without the need for extra ground stations on Earth. [21][23][30]

9 TDRS sit about 35,400 km above the Earth

ORBITS, briefly

• Every satellite must have an orbital path (spacecraft that travel into deep space to look at distant planets, such as NASA's New Horizons, are space probes not true satellites).
• After a satellite is launched to space, it needs little to no power to keep it moving.
• The orbit reached is a combination of the satellite's velocity and the force of the Earth's gravitational pull on the satellite. [39]

Satellites in Low Earth orbit follow an elliptical path below 2,000 km. They circle the Earth at great speeds (~17,000 mph) to counter gravity's pull. [3][28] They complete one revolution around the Earth in 88 to 127 minutes. [41]

GPS satellites in medium Earth orbit

Medium Earth orbit is any orbit between 2,000 km - 35,786 km.

Satellites in medium Earth orbit complete one revolution of the Earth in 127 minutes to 24 hours. [41]

High Earth orbit is any orbit higher than 35,786 km. 

Image Credit: www.mpoweruk.com 

Satellites in geosynchronous orbit (blue) have an altitude of approximately 35,786 km above sea level, and return to the same position in the sky after each sidereal day (~ 24 hours). [31][41]

Two Satellites in Geostationary orbit

A geostationary orbit  is a type of geosynchronous orbit. [31][41]

Geostationary orbit puts the satellite in a position where it is always directly above the same spot on the planet at all times, meaning that ground-based antennas can remain fixed in one direction. [31]

To an observer on the earth, a satellite in a geostationary orbit appears motionless, in a fixed position in the sky. This is because it revolves around the Earth at the Earth's own angular velocity (360 degrees every 24 hours, in an equatorial orbit). [32]

Image Credit: www.thetech.org

A Polar orbit is one in which a satellite passes from North to South above or nearly above both poles of the Earth on each revolution, enabling satellites to scan the entire Earth's surface. 

Polar orbits are often used for earth-mapping, reconnaissance satellites, as well as for some weather satellites. [33-34]

A commonly used altitude for Polar orbit is approximately 1000 km, in which the satellite laps the Earth in about 100 minutes. [35]

Travelling from the North to the South poles, satellites in sun-synchronous orbit pass over the same part of Earth at approximately the same local time each day. [36] 

"For the Terra satellite for example, it’s always about 10:30 in the morning when the satellite crosses the equator in Brazil. When the satellite comes around the Earth in its next overpass about 99 minutes later, it crosses over the equator in Ecuador or Colombia at about 10:30 local time." [37]

The dark red arrow mark the most recent of three consecutive sun-synchronous orbitsImage Credit: earthobservatory.nasa.gov

Satellites in sun-synchronous orbit are useful in collecting imaging and weather/climate data as they can track change over time. 

Image Credit: www.esa.int

SPACE DEBRIS

Space debris is the collection of defunct objects in orbit around Earth. This includes spent rocket stages, old satellites and fragments from disintegration, erosion and collisions, dust from solid rocket motors, and paint flakes. [14]

It is estimated that there are 300,000 pieces of space junk ranging from 1 cm to 25 cm, and that on average, one satellite is destroyed each year. [15]

"Kessler syndrome is a scenario in which the density of objects in low Earth orbit (LEO) is high enough that collisions between objects could cause a cascade—each collision generating space debris that increases the likelihood of further collisions." [16-18] 

"One implication is that the distribution of debris in orbit could render space exploration, and even the use of satellites, unfeasible for many generations." [16-18] 

An average of one cataloged piece of debris has fallen back to Earth each day for the past 50 years. [19]

The two main debris fields are the ring of objects in geosynchronous orbit
and the cloud of objects in low Earth orbit.

The Space Shuttle Endeavour (2007) had a major impact on its radiator.

HOW SATELLITES GO TO THERE



Delta IV on the launchpad at Cape Canaveral with the Air Force's WGS-4 payload. [38]

 Credit: Pat Corkery, United Launch Alliance



Illustration depicting the components of the Delta IV Medium+ (5,4) rocket. [31]

Credit: United Launch Alliance

What follows is my extremely simplified version of the play-by-play for Delta IV launch on January 14, 2012: (Derived from space.com's Air Force Ready For Big Launch From Florida Tonight, spaceflightnow.com's  WGS 4 Launch Timeline, and the Air Force/United Launch Alliance.)

• The main engine begins to ignite as the liquid hydrogen fuel valve is opened, creating a large fireball at the base of the rocket. The engine powers up to full throttle for a computer-controlled checkout before liftoff.

• Delta IV lifts off from the launch pad at Cape Canaveral.

• The vehicle heads downrange, arcing over the Atlantic.

• Having used up all their solid-propellant, the two strap-on boosters are shed.

• The composite material protecting the payload during ascent is shed.

• The main engine continues its firing through the initial 4 minutes of the launch by consuming liquid hydrogen and liquid oxygen to climb beyond the edge to space.

• Having accelerated the rocket in excess of 11,000 mph, the Common Booster Core is shed.

• The main engine then ignites for a 16 minute firing that propels the vehicle into an elliptical parking orbit.

• Engine cutoff comes over the mid-Atlantic nearly 3,200 miles downrange at a speed of 20,100 mph.

• After a short coast period, the upper stage is reignited to raise the orbit to the planned altitude for deploying the satellite.

• At 40 minutes and 32 seconds after liftoff, the satellite is released into space from the Delta IV rocket and will use its on-board propulsion to reach geostationary orbit where it will match Earth's rotation and appear fixed above the equator to cover the Middle East and Southeast Asia.

The Delta IV launch can be viewed on Youtube. I chose the April 2014 Soyuz launch (below) because an on board camera recorded the rocket's ascent, the release of the satellite and the beginning of its orbit around Earth. 

 

European Space Agency, ESA              

RELATED VIDEO LINKS

Invisible Universe Revealed. Hubble's 25th Anniversary - NEW2015 Documentary

How To Build A Satellite BBC Documentary 2013

The Satellites - How Satellite Works - History Documentary Film

A Year in Space: The Mission | TIME

MIR Space Station collision

Landing on a Comet - The Rosetta Mission

New Horizons

***

FIN

REFERENCES

[1] http://www.oxforddictionaries.com/definition/english/satellite

[2] Rhodes, Richard (2000). Visions of Technology. Simon & Schuster. p. 160. ISBN 978-0-684-86311-5.

[3] https://en.wikipedia.org/wiki/Satellite

[4] Gray, Tara; Garber, Steve (2 August 2004). "A Brief History of Animals in Space".NASA.

[5] http://time.com/3546215/laika-1957/

[6] Chang, Alicia (30 January 2008). "50th anniversary of first U.S. satellite launch celebrated". SFGate. Associated Press. Archived from the original on 2008-02-01.

[7]  "Orbital Debris Education Package" (PDF). Lyndon B. Johnson Space Center. 

[8]http://www.universetoday.com/42198/how-many-satellites-in-space/

[9] Grant, A.; Meadows, J. (2004). Communication Technology Update (ninth ed.). Focal Press. p. 284. ISBN 0-240-80640-9.

[10]  "Conventional Disposal Method: Rockets and Graveyard Orbits". Tethers.

[11]  "FCC Enters Orbital Debris Debate". Space.com.

[12] "Sputnik 1 – NSSDC ID: 1957-001B". NSSDC Master Catalog. NASA.

[13] https://en.wikipedia.org/wiki/Sputnik_1

[14] https://en.wikipedia.org/wiki/Space_debris

[15]  "Lockheed Martin in space junk deal with Australian firm". BBC News. 28 August 2014.

[16] Kessler 1991, p. 63.

[17] Bechara J. Saab, "Planet Earth, Space Debris", Hypothesis Volume 7 Issue 1 (September 2009).

[18] Donald J. Kessler and Burton G. Cour-Palais (1978). "Collision Frequency of Artificial Satellites: The Creation of a Debris Belt". Journal of Geophysical Research 83: 2637–2646.Bibcode:1978JGR....83.2637K. doi:10.1029/JA083iA06p02637.

[19]  Brown, M. (2012). Orbital Debris Frequently Asked Questions. Retrieved from http://orbitaldebris.jsc.nasa.gov/faqs.html.

[20] https://en.wikipedia.org/wiki/Communications_satellite

[21] https://en.wikipedia.org/wiki/Tracking_and_Data_Relay_Satellite_System

[22] http://www.britannica.com/technology/satellite-communication

[23] http://satellites.spacesim.org/english/function/communic/index.html

[24]https://www.nasa.gov/directorates/heo/scan/communications/outreach/funfacts/txt_passive_active.html

[25] http://www.nrcan.gc.ca/earth-sciences/geomatics/satellite-imagery-air-photos/satellite-imagery-products/educational-resources/14639

[26] http://www.seos-project.eu/modules/remotesensing/remotesensing-c02-p02.html

[27] http://www.asc-csa.gc.ca/eng/satellites/radarsat2/applications.asp

[28] http://www.infoplease.com/encyclopedia/science/satellite-artificial-types-satellites.html

[29] http://www.satellites.spacesim.org/english/anatomy/ttc/telemetr.html

[30] www.nasa.com 

[31] satellites.https://en.wikipedia.org/wiki/Geosynchronous_satellite

[32] https://en.wikipedia.org/wiki/Communications_satellite

[33] https://en.wikipedia.org/wiki/Polar_orbit

[34] Science Focus 2nd Edition 2, pg. 297

[35] "Polar Orbiting Satellites". Dr. David P. Stern. 2001-11-25.

[36] http://satellites.spacesim.org/english/anatomy/orbit/sunsynch.html

[37] http://earthobservatory.nasa.gov/Features/OrbitsCatalog/page2.php

[38] http://www.space.com/14276-air-force-rocket-launch-thursday-satellite.html

[39] http://www.satellites.spacesim.org/english/anatomy/orbit/index.html

[40] http://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-the-hubble-space-telecope-k4.html

[41] http://www.mpoweruk.com/satellites.htm

ADDITIONAL RESOURCES

The International Space Station Spot the Station

N2YO.com real-time satellite tracking

http://www.nasa.gov/

http://www.asc-csa.gc.ca/eng/

http://www.esa.int/ESA

http://en.federalspace.ru/

http://hubblesite.org/

http://weather.gc.ca/satellite/index_e.html

space.com

List of Spacecraft Manufacturers

spacex.com

lockheedmartin.ca

IMAGE CREDITS

"AEHF 1" by USAF (Los Angeles AFB) - http://www.losangeles.af.mil/art/media_search.asp?q=aehf&btnG.x=0&btnG.y=0 [1]. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:AEHF_1.jpg#/media/File:AEHF_1.jpg

"Laika". Licensed under Fair use via Wikipedia - https://en.wikipedia.org/wiki/File:Laika.jpg#/media/File:Laika.jpg

SSL 1300 Satellite Overview  www.sslmda.com

"Hubble First Servicing EVA - GPN-2000-001085" by NASA - Great Images in NASA Description. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Hubble_First_Servicing_EVA_-_GPN-2000-001085.jpg#/media/File:Hubble_First_Servicing_EVA_-_GPN-2000-001085.jpg

“Echo - A Passive Communications Satellite - GPN-2002-000122” von NASA - Great Images in NASA Description. Lizenziert unter Gemeinfrei über Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Echo_-_A_Passive_Communications_Satellite_-_GPN-2002-000122.jpg#/media/File:Echo_-_A_Passive_Communications_Satellite_-_GPN-2002-000122.jpg

“Tracking and Data Relay Satellite” by www.nasa.gov

"ConstellationGPS" by Original uploader was El pak at en.wikipedia - Transferred from en.wikipedia. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:ConstellationGPS.gif#/media/File:ConstellationGPS.gif

“Geosynchronous and Geostationary Orbits” by www.mpoweruk.com 

"Geostationaryjava3Dsideview" by Lookang many thanks to author of original simulation = Francisco Esquembre author of Easy Java Simulation = Francisco Esquembre - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Geostationaryjava3Dsideview.gif#/media/File:Geostationaryjava3Dsideview.gif

“Polar Orbit gif” by www.thetech.org

“Sun-synchronous Orbits” by  earthobservatory.nasa.gov

“Polar, Sun-synchronous and Geo-stationary Orbits” by www.esa.int

"Debris-GEO1280" by [[user:]] - NASA Orbital Debris Program Office, photo gallery. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Debris-GEO1280.jpg#/media/File:Debris-GEO1280.jpg

"STS-118 debris entry" by NASA - http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080010742_2008009999.pdf. Licensed under Public Domain via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:STS-118_debris_entry.jpg#/media/File:STS-118_debris_entry.jpg

“Delta IV on Launchpad at Cape Canaveral” by Pat Corkery, United Launch Alliance via www.space.com

“Illustration Depicting the Components of the Delta IV Medium+ (5,4) rocket” by United Launch Alliance via www.space.com