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Small could be the next big thing in satellite tech
It happened with our desktop computers shrinking into laptops and palm-sized gadgets and our mobile phones getting tinier. In the satellite industry too, ‘small’ could be the next big thing in the coming years.
A small satellite can equally suit communications, earth observation or surveillance, disaster monitoring or scientific experiments — the jobs that its bigger cousins do. It would weigh a few hundred kilos versus the 2-to-10-tonne giants that circle the earth today.
‘Smallsats’ cost less, weigh less, can be built fast and launched quickly in multiples and pack in just as much punch, according to Mr D.V.A. Raghav Murthy, ISRO’s Project Director for Small Satellites.
“They can achieve 90 per cent of what big satellites can at five per cent of the cost and do 17 per cent of their tasks at one per cent of the cost,” Mr Koteswara Rao, Director, Laboratory for Electro-Optics Systems at ISRO, corroborated.
A growing number of Governments, companies and user industries built around them are apparently warming up to their charms.
If India has had its IMS-1 and the upcoming IMS-2, both carrying the latest technologies in earth observation, Russia, the US and Israel are known to have small, short-life military spy satellites that can be quickly put into orbit.
Classed as nano or piko; micro (up to 100 kg) or mini (up to 500 kg), or the 10-cm ‘cubesats’, small sats cost under Rs 1 crore in India compared to Rs 200-300 crore for larger 2-tonne class satellites, Mr Murthy said at a session on small satellites at the Bengaluru Space Expo here.
Universities are eyeing smallsats as good educational tools for engineering students. ISRO, which recently launched StudSat, one such student satellite by Karnataka and Andhra Pradesh engineering students, has got inquiries from 22 institutions/universities and is trying to tell them to team up rather than each have a satellite.
IIT-Kanpur’s Jugnu and IIT-Bombay’s Pratham are in the pipeline, while Anna University’s Anusat was the first such Indian student satellite to go into orbit.
ISRO has launched many small satellites mainly for experimental purposes such as remote sensing, atmospheric studies, payload development, orbit control and recovery technology.
Dr Susmita Mohanty, Mumbai-based founder and CEO of space start-up Earth2Orbit India Pvt Ltd, said nano and small satellites for various purposes were showing a growth rate of at least 30 per cent a year led by the US and there would be 415 satellites in a near-earth orbit by 2014.
Earth2Orbit, which is an informal overseas marketing associate for ISRO’s earth imageries, also wants to bring in small satellites to be launched on the PSLV, which is emerging as a favourite in this band, she said. The smallsat launch business was pegged at $160 billion a year and the Indian workhorse launcher, she said, should capture at least 20 per cent of this business. Businesses are building around small sats. SSTL or Surrey Satellite Technology Ltd, the dedicated smallsat company now owned by Europe’s spacecraft major EADS Astrium, is building a small 200-kg spacecraft for Kazakhstan to support land mapping and resource management and planning. Launch majors such as Space X are eyeing these opportunities.
Dubai’s eye high in the sky
In a small room on the outskirts of Dubai at the Emirates Institute for Advanced Science and Technology (EIAST), a large television screen shows a countdown in seconds.
Other screens show an array of maps, sensor readings and other mathematical data.
This is mission control for DubaiSat-1. The satellite, which was launched in July last year, is the Emirates’ first remote imaging satellite and one of the major projects in the UAE’s emerging space industry.
In a few seconds, the satellite will cross over the Gulf and provide a window for engineers to download important image data. As the satellite orbits 690km above Earth, time is of the essence.
Back on Earth, Salem Humaid al Marri, the space programme project manager for EIAST, walks over to a computer monitor that displays raw images from the satellite in basic black and white.
“Ah, it’s no good,” he says, pointing at a group of seemingly innocuous white dots next to what appears to be the cluster of man-made islands called the World.
“See that? Those are clouds. Any obstruction ruins the image and we can’t really use them.”
Apart from when someone is trying to locate their house, satellite imagery may not seem interesting. But each image can be analysed in a variety of ways, giving users including scientists and urban planners a bird’s-eye view of what is going on.
After its launch from Baikonur in Kazakhstan, DubaiSat-1 was immediately put to work beaming down images of Dubai. UAE universities have used imagery from the satellite for such purposes as monitoring shoreline erosion.
The satellite is a geek’s dream, filled with space-ready gadgets such as accelerometers, gyroscopes, antennas, cameras and solar energy panels.
Surprisingly, the on-board computer that manages camera imagery data is 15 years old, and the processor is just powerful enough to perform key tasks.
While providing satellite imagery to the Dubai Government is the main business of DubaiSat-1, commercial applications are being discovered. Mr al Marri points out that companies are increasingly approaching EIAST to request certain images as well as leasing time on the institute’s terrestrial antenna in case there is immediate need for data from another satellite orbiting over Dubai.
“Our goal is not to go commercial, but if there’s a chance to commercialise our data, it’s a bonus. Our goal is to serve the government needs in terms of what the municipality wants,” Mr al Marri says. “But if you’re dedicated to commercialisation and you’ve got a satellite, you can make a lot of money.”
For now, the US$50 million (Dh183.7m) satellite project is a vital part of the UAE’s space plans in what is expected to be a major industry in the Emirates during the next 20 years.
The UAE already has Thuraya, a telecommunications company with two orbiting satellites relaying voice and broadband data. The company plans next year to launch Yahsat, an internet and television satellite aimed at covering the Middle East and Africa.
Aabar Investments, which is owned by the Abu Dhabi Government, has also moved into the space business. The company has taken a 32 per cent stake in Virgin Group’s commercial space enterprise, Virgin Galactic, at a cost of about $280m and holds the exclusive regional rights for any Virgin spaceport that is to be built here.
“If you look at the UAE in terms of the region, it’s one of the most advanced economies when it comes to space technology,” Mr al Marri says, adding that the future for the DubaiSat programme is bright. Two more satellites are scheduled to be added to EIAST’s fleet during the next five years, with the second to be built entirely in Dubai.
The new satellites will have better picture resolution, greater data transmission capacity and propulsion systems to allow mission control to change their orbits.
“The main aspect of the DubaiSat project was technology transfer,” Mr al Marri says. “For the first model, we sent … engineers to South Korea and they worked on all aspects of the satellite from design to launch. So we’re trying to gain these skills and give UAE nationals the opportunity to come back to Dubai and build better satellites.”
Introduction to Earth Station Antenna
Antenna attaches much importance in the earth station, the antennas are divided into different categories, and this article mainly introduces Cassegrain Tx/Rx antenna and the working principle of earth station antenna.
Earth station antenna is an important part in the Satellite communication earth stations. The antenna mainly does the energy transformations between electric energy of alternating electro circuit and electromagnetic wave in the space. According to the required operational frequency, polarization and direction transmit and receive signals, and equivalently amplify the transmitting power and receiving power.
According to the antenna geometry, in the earth station there are axial symmetry and no axial symmetry antenna structures. At present in the actual application there is truss antenna structure, kingpost antenna, turntable antenna mount…etc. According to the function and application it can be classified as full motion antenna, limit motion antenna, vehicle mounted antenna, Marine antenna, portable antenna…etc. Blow takes the Cassegrain antenna as example, introducing the working principle and technical specification for the earth station antenna.
Working Principle
Cassegrain antenna is a dual reflector antenna with the symmetric form of rotary axes and it consists of main reflector, sub-reflector and feed. Main reflector is parabolic of revolution, sub-reflector is hyperboloid of revolution, and feed is horn radiator. One of the focus points in the hyperboloid of revolution locates on the focus point of the parabolic; another point locates on the phase center of the feed. The result that sphere electromagnetic wave from the feed is transmitted by the hyperboloid of revolution is the same as the sphere electromagnetic wave from the focus of parabolic irradiates the parabolic; and then reflect by the parabolic once again to form the electromagnetic wave beam equivalent to the parabolic and proceed along the axial direction of the main reflector. Thus transfer the sphere wave to the plane wave and form the narrow beam, and then radiate to the space. According to the antenna reciprocity principle, the process that the antenna receive the electromagnetic wave is converse to the one that the antenna transmit the electromagnetic wave. Generally the Cassegrain antenna efficiency is 50%-60%, Modified Cassegrain antenna improve the antenna efficiency further, now modified Cassegrain antenna is popular.
Earth station antenna capture the Satellite signal and tracking system track the signal together at the same time, after the receiving signal from the feed is low-noise amplified, and then it will be sent to earth station equipment for demodulation processing. Power splitter sends one way of signal to tracking receiver, tracking receiver receive beacon signal and output a DC voltage which is in proportion to the strength of the RF signal level. According to DC signal from beacon receiver the antenna control unit (ACU) control the azimuth and elevation motorized controller, until the DC signal becomes Maximum so that earth station can receive the Satellite signal steadily.
Specification
Take ANTESKY 4.5m earth station antenna as example, Antesky Science Technology Inc. is specially engaged in designing, manufacturing and installing satellite communication antennas and relevant servo equipments. Ante-sky can offer a complete line of earth station antenna products and systems, such as VSAT antennas, Tx/Rx antennas, TV receive only antennas, satellite news gathering Antennas, Flyaway, antenna control system and tracking system.