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laser broadband from nasa semin ppt
Post: #1
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Abstract
Lasers have been considered for space
communications since their realization in 1960.
Specific advancements were needed in
component performance and system engineering
particularly for space qualified hardware.
Advances in system architecture, data formatting
and component technology over the past three
decades have made laser communications in
space not only viable but also an attractive
approach into inter satellite link applications.
Information transfer is driving the requirements
to higher data rates, laser cross -link technology
explosions, global development activity,
increased hardware, and design maturity. Most
important in space laser communications has
been the development of a reliable, high power,
single mode laser diode as a directly modulable
laser source. This technology advance offers the
space laser communication system designer the
flexibility to design very lightweight, high
bandwidth, low-cost communication payloads for
satellites whose launch costs are a very strong
function of launch weigh.
This feature substantially reduces blockage of
fields of view of most desirable areas on
satellites. The smaller antennas with diameter
typically less than 30 centimeters create less
momentum disturbance to any sensitive satellite
sensors. Fewer on board consumables are
required over the long lifetime because there are
fewer disturbances to the satellite compared with
heavier and larger RF systems. The narrow beam
divergence affords interference free and secure
operation.
Background
Until recently, the United States government was
funding the development of an operational space
laser cross-link system employing solid-state
laser technology. The NASA is developing
technology and studying the applicability of space
laser communication to NASA's tracking and
data relay network both as cross-link and for
user relay links. NASA's Jet Propulsion
Laboratory is studying the development of large
space and ground-base receiving stations and
payload designs for optical data transfer from
interplanetary spacecraft. Space laser
communication is beginning to be accepted as a
viable and reliable means of transferring data
between satellites. Presently, ongoing hardware
development efforts include ESA's Space satellite
Link Experiment (SILEX) and the Japanese's
Laser Communication Experiment (LCE).
The United States development programs ended
with the termination of both the production of the
laser cross-link subsystem and the FEWS
satellite program. Satellite use from space must
be regulated and shared on a worldwide basis.
For this reason, frequencies to be used by the
satellite are established by a world body known
as the International Telecommunications Union
(ITU) with broadcast regulations controlled by a
subgroup known as World Administrative Radio
Conference (WARC). An international consultative
technical committee (CCIR) provides specific
recommendations on satellite frequencies under
consideration by WARC.
The basic objective is to allocate particular
frequency bands for different types of satellite
services, and also to provide international
regulations in the areas of maximum radiation's
level from space, co-ordination with terrestrial
systems and the use of specific satellite locations
in a given orbit. Within these allotments and
regulations an individual country can make its
own specific frequency selections based on
intended uses and desired satellite services.
[b[/b]
Post: #2
NASA introduced a process of accommodation in a space through the laser communication relay. NASA's laser broadband features a terminal payload on board a Loral satellite that will be launched in 2016. It will be the commercial satellite that will provide the size, power system and location to implement the space laser communication. Through this technology, the data rate potential increases to 100 times more than the traditional form of radio frequency that has much less power and mass.

When NASA's Lunar Laser Communication Demonstration (LLCD) begins operating on board the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission managed by NASA's Ames Research Center in Moffett Field, California, it will attempt to show bidirectional laser communication beyond the Earth, expanding the possibility of transmitting large amounts of data. This new capability could one day allow high-definition 3-D video transmissions in deep space to become routine.

"The objective of the LLCD experiment is to validate and build confidence in this technology for future missions to consider using it," said Don Cornwell, manager of LLCD. "This unique capability developed by MIT (Lincoln Laboratory of the Massachusetts Institute of Technology) has incredible application possibilities and we are very excited about the implementation of this instrument."

Since NASA first ventured into space, through moon landings, the shuttle program and unmanned exploration missions, radio frequency communication, also known as RF, has been the communication platform used. But RF is reaching its limit just when the demand for more data capacity continues to rise. The development of laser communications will give NASA the ability to expand communication applications, such as higher image resolution and even 3-D video transmission in deep space.

LLCD is NASA's first dedicated system for bidirectional communication using lasers instead of radio waves. "LLCD is designed to send six times more data from the moon using a smaller transmitter with 25 percent less energy compared to the next-generation radio (RF) system," said Cornwell. "Lasers are also safer and less susceptible to interference and jamming."

The LLCD experiment takes place aboard NASA's LADEE: a 100-day robotic mission designed, built, integrated, tested and operated by Ames. LADEE will try to confirm if the dust caused a mysterious glow on the lunar horizon that astronauts observed during several Apollo missions and explore the moon's tenuous and exotic atmosphere. The launch of the LADEE spacecraft is scheduled for September aboard a Minotaur V rocket from the US Air Force, a ballistic missile converted into a spacecraft and operated by Orbital Sciences Corp. of Dulles, Va., From the Wallops flight facility of NASA on Wallops Island. Virginia.

The LADEE spacecraft will take 30 days to reach the moon due to its flight path. LLCD will begin operations shortly after reaching the lunar orbit and will continue for 30 days afterwards.

The main objective of LLCD's mission is to transmit hundreds of millions of bits of data per second from the moon to Earth. This is equivalent to transmitting more than 100 HD television channels simultaneously. The ability to receive LLCD will also be tested as tens of millions of bits per second are sent from Earth to the spacecraft. These demonstrations will demonstrate that the technology to increase bandwidth for future missions is possible.

There is a primary ground terminal at NASA's White Sands Complex in New Mexico, to receive and transmit LLCD signals. The MIT team designed, built and tested the terminal. They will also be responsible for the operation of LLCD on that site.

There are two alternative sites, one located at NASA's Jet Propulsion Laboratory in California, which is just to receive. The other is being provided by the European Space Agency on the Spanish island of Tenerife, off the coast of Africa. Will have bidirectional communication capability with LLCD. "Having multiple sites gives us alternatives that greatly reduce the possibility of cloud interference," Cornwell said.
 

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