physics

Lincoln Experimental Satellite

Lincoln Experimental Satellite is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lincoln Experimental Satellite rather than just read about it. In short: The Lincoln Experimental Satellite series was designed and built by Lincoln Laboratory at Massachusetts Institute of Technology between 1965 and 1976, under USAF sponsorship, for testing devices and techniques for satellite communication. Development After the successful development and deployment of Project West Ford, a passive communications system consisting of orbiting copper needles, MIT's Lincoln Laboratory tu…

Key takeaways

Lincoln Experimental Satellite belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lincoln Experimental Satellite to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lincoln Experimental Satellite from memory before moving on to harder problems.

Reference excerpt

The Lincoln Experimental Satellite series was designed and built by Lincoln Laboratory at Massachusetts Institute of Technology between 1965 and 1976, under USAF sponsorship, for testing devices and techniques for satellite communication.

Development After the successful development and deployment of Project West Ford, a passive communications system consisting of orbiting copper needles, MIT's Lincoln Laboratory turned to improving active-satellite space communications. In particular, Lincoln aimed to increase the transmission capability of communications satellites ("downlink"), which was necessarily constrained by their limited size. After receiving a charter in 1963 to build and demonstrate military space communications, Lincoln focused on a number of engineering solutions to the downlink problem including improved antennas, better stabilization of satellites in orbit (which would benefit both downlink and "uplink"—communications from the ground), high-efficiency systems of transmission modulation/de-modulation, and cutting-edge error-checking techniques. These experimental solutions were deployed in a series of nine spacecraft called Lincoln Experimental Satellites (LES). Concurrent with their development, Lincoln also developed the Lincoln Experimental Terminals (LET), ground stations that used interference-resistant signaling techniques that allowed use of communications satellites by up to hundreds of users at a time, mobile or stationary, without involving elaborate systems for synchronization and centralized control. The 1st, 2nd, and 4th satellites in the LES series were designated "X-Band satellites," designed to conduct experiments in the X band, the military's super high frequency (SHF) band (7 to 8 GHz) because solid-state equipment allowed for comparatively high output in this band, and also because the band had been previously used by West Ford.

Overview

The series had satellites named LES-1 through LES-9. They suffered a number of launch problems - LES-1 and LES-2 were supposed to be delivered to the same 2,800 x 15,000 km orbit, though a failure of a boost stage left LES-1 in a 2,800 km circular orbit. LES-3 and LES-4 were intended to be delivered to geostationary orbit, but a launch problem left them in their transfer orbit. All these satellites returned useful results despite the incorrect orbits. LES-5, -6, -8 and -9 ended up successfully in geostationary orbit; the project that would have been LES-7 ran out of funding and was cancelled. [LES-9 was in an elliptical orbit in the mid-1980s and was used by environmental buoys to communicate data out of the very high northern latitudes. (Geostationary satellites are not visible at those latitudes as they are below the horizon.)] LES-3 was a very small (16 kg) satellite containing a radio transmitter, intended to measure the extent of multi-path interference due to reflection of 300 MHz radio waves off sufficiently flat parts of the Earth. Amongst the technologies tested on LES-1 through LES-4 were solid-state X-band radio equipment, low-power logic circuits, electronic despinning (using optics to determine the location of the Earth and Sun relative to a spinning satellite at any moment, and then transmitting via whichever of several antennae were best positioned with respect to the Earth), and magnetic torquers. LES-8 and LES-9 were satellites of around 450 kg mass, launched on March 14, 1976. They were originally planned to be equipped with pulsed plasma engines but actually launched with gas thrusters; unusually for communication satellites, they are powered by MHW-RTGs rather than by solar panels. There was a cross-link between them in the 36–38 GHz part of the K band, with UHF up- and down-links; and the cross-link technology demonstrated was the basis for current inter-satellite communications used by numerous satellites. The original intention was to run the cross-link at a frequency in the 55–65 GHz range, which is absorbed by water, so that it would be impossible for Earth-based receivers to pick up scattered signals, but technology at the time was inadequate. They operated in geostationary orbit until 1992 and now are drifting slowly. Lincoln Laboratory's next satellite-communication project after LES was the construction of FLTSAT EHF Packages.

LES Missions

Current status

Amateur radio enthusiasts were able to detect the radio signals emitted from LES-1 at the end of 2012 and the telemetry of LES-5 in 2020. LES-9 was decommissioned in 2020 after 44 years of service, whilst LES-8 was decommissioned in 2004.

References

NASA SP-4217 Beyond the Ionosphere (derived from William W. Ward, Franklin W. Floyd (1989), Thirty Years of Space Communications Research and Development at Lincoln Laboratory) is a detailed description of satellite communications development at Lincoln Laboratory, and was used as a reference for much of this article.

See also Voyager Program (also used MHW-RTGs, which operated into the 21st century)

Illustrations

Lincoln Experimental Satellite: LES-4 — LES-4

Lincoln Experimental Satellite: Launch of the Titan IIIA rocket with satellite Lincoln Experimental Satellite 1. — Launch of the Titan IIIA rocket with satellite Lincoln Experimental Satellite 1.

Worked examples

Example 1 — a first encounter with Lincoln Experimental Satellite

Start with the simplest possible case. Write down what Lincoln Experimental Satellite claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lincoln Experimental Satellite before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lincoln Experimental Satellite ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lincoln Experimental Satellite

In research: Lincoln Experimental Satellite appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lincoln Experimental Satellite in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lincoln Experimental Satellite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Communications satellites, Lincoln Experimental Satellite, Massachusetts Institute of Technology, so understanding it makes those chapters shorter.
In everyday life: Look for Lincoln Experimental Satellite outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Lincoln Experimental Satellite in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lincoln Experimental Satellite means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lincoln Experimental Satellite out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lincoln Experimental Satellite in simple terms?

Why does Lincoln Experimental Satellite matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lincoln Experimental Satellite?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lincoln Experimental Satellite.