Skip to main content

A Quick Supplement For Understanding The Role and Context Of Anti-Satellite Weapons By Lt Gen P.R. Shankar










A satellite can be used for many military purposes. Primarily, military satellites are used for Communication, Intelligence, Surveillance & Reconnaissance, Navigation, Meteorological Observations and Electronic Warfare. Theoretically any satellite, can carry out these functions whether it is in High, Geostationary, Mid or Low Earth orbits. However, from a practical point of view it is the Low Earth Orbit (LEO) which is most commonly used for military satellites. It is highlighted at the outset that understanding LEO is more important for exploiting space rather than knocking a satellite down. The LEO is the simplest, cheapest and safest location for the deployment of satellites, space stations, and crewed space missions. Most military personnel do not understand the fundamentals of a LEO and hence are at a loss to appreciate the essentials of ASAT tests and their implications. In this context this article is an attempt to give readers a basic understanding of LEOs and their utility as military platforms.


Height






A Low Earth Orbit Satellite is one that is in orbit 160 -2000 km above the earths surface. Any object below 160 Km suffers from a phenomenon called orbital delay and descends into the atmosphere to burn or crash land. In practice, LEO satellites orbit between 300 -1000km. The reason being that below 300m the drag is high, and it is difficult to maintain a satellite at that altitude. Above 1000m there are something called Van Allen radiation belts which are zones of charged particles. They cause a lot of ionospheric interference and endanger satellites which invariably have sensitive equipment. A major factor in deciding the height of the satellite is the bandwidth available for operations and the latency (communications time lag). A LEO satellite gives the best results for this.

 Orbits, Polarity and Speed





LEO satellites can also be on an equatorial orbit, inclined orbit or a polar orbit. In an equatorial orbit, the area covered is a latitudinal band only. Normally LEO satellites are kept in Polar or Inclined orbits which enables max coverage of the Earth. A polar orbit is essentially a north south orbit around the poles. The earth revolves west to east. The satellite orbit and the earth’s rotation allow it to cover most of the earth surface after it has covered a complete cycle of orbits in a certain period.  Orbits can be circular or elliptical. Circular orbits are popular, because then the satellite is at a constant altitude requiring a constant strength signal to communicate. Elliptical orbits are useful to increase the stay period over an area.  
LEO satellites orbit the earth at an average speed of 7.8 Km/ sec when their altitude is 300 km. As the altitude increases to about 1500 km, the speed reduces to 7.12 km/sec. They circumvent the Earth in 90 minutes to 120 minutes (approx.). It means that a LEO satellite circumvents the earth 16-12 times a day depending upon the height at which it is placed. Lower the orbit height, higher is the number of orbits and vice versa. As a thumb line guide, a LEO satellite will traverse the entire length of Pakistan (north to south) in about 7-8 minutes. By the time the satellite finishes one orbit of 90 minutes, Pakistan would have passed by underneath. Some part of Iran would be directly below the satellite. Twelve hours later, Pakistan will be once again under the satellite for about 7-8 minutes. Hence in a 24-hour period, Pakistan would have been seen for 14-16 minutes.        









Footprint


















Every satellite has a footprint or the area it covers on the surface of the Earth which is directly proportional to its orbital height. As the satellite passes over the Earth, the location of the footprint changes. The continuous path of the footprint is called a Swath. The Satellite A has a larger foot print than Satellite B as shown in the diagram. Hence higher the satellite, greater the foot print. A corollary to this is that, with increase in height and decrease in speed, the satellite stays over the target area for a longer time. Its ability to stay and stare over a larger area increases.   As compared to a Geostationary orbit, which has a large footprint which is stationary, a LEO satellite has a small and momentary footprint and can observe / communicate with only a fraction of the Earth at a time. In order to overcome this issue of interrupted coverage LEO satellites are used in a constellation to provide continuous coverage.






















Launching

Satellites are placed in space by launching a rocket. The higher the height at which a rocket is placed the greater the effort required.  Which means a heavy rocket and extensive launching facilities. A LEO satellite requires a very small rocket in comparison to a Geostationary rocket. Also, LEO satellites and space stations are more accessible for crew and servicing.

Segments

Any Satellite system has a space segment and an earth segment. The space segment consists of the sensor, satellite, power, transmission and control sub systems. Control sub system will be controls of the satellite as well as the sensor. Sensors can be steered, directed or focused as required. The Earth segment consists of the tracking antenna, transmission, downlink/ data receivers, sensor control and orbit control sub systems. The overall mission control also forms part of the Earth Segment.   



  



















Sensors

A satellite is essentially a platform in space which hosts a payload. Theoretically, a LEO satellite can carry any number of sensors as part of its payload. However due to considerations of launch capabilities and on-board power requirement, the sensors are restricted. More sensors imply greater weight. Greater weight implies a more powerful launch. Similarly, power is required to operate the sensors and the satellite controls. A complex sensor needs greater power.  As the height increases, the amplifier power requirements increase for signal transmission. This in turn demands more on-board power. Satellites draw solar power and operate with it.  To that extent, a LEO in polar orbit is well suited since it is in sun for fifty percent of its orbit and gets recharged repeatedly. However overall power available is a severe limitation. Another aspect is that for a given sensor while the footprint increases with height, the power requirement also increases, and resolution detail decreases. So, this contradictory phenomenon must be reconciled.  A major factor is the technology adopted on the sensors. Advanced sensor technologies reduce sensor size, power requirements and weight. This enhances the capability of the satellite. A sensor could be active or passive. A passive sensor uses an external source of energy or the target emissions for detection. An active sensor generates its own energy to either illuminate the target or act upon it. Any satellite will have dedicated and separate communication channels for controlling the satellite, controlling each of the sensors and downloading data from the sensors. 
Passive Sensors

Most military sensors fall in the passive category. They use the illumination by the sun or the emissions by the target to detect them. Battle field sensors such as day/night cameras, Thermal Imaging systems, electronic warfare receivers, communication transponders, and meteorological are all passive systems. Communication transponders can be used for Command and Control, Air Space Management, UAV/ Air craft control and enhancing range of communications. 
  
Active Sensors

Active systems are more complex since they must generate some energy to act on the target. Active sensors include any Radars to include Synthetic Aperture Radars, LIDARs, laser-based devices, electronic emissions for jamming, and Directed Energy Weapons the biggest challenges in an active system is power generation and management and weight management. It must be remembered that energy generation consumes weight and power at a phenomenal rate. In this context, though satellites are spoken of as platforms for Directed Energy Weapons, technologically we are not yet there. USA started the Star Wars Program in the Ronald Reagan era and had to close it down since it was prohibitively costly.     



 he LEO environment is becoming congested with space debris because of the frequency of object launches

Comments

  1. We are cheap Off Page SEO Services provider through the backlinks technique. Our services are affordable for every one you can order us anytime. Our team includes well organized persons. For order you can visit my gig.

    ReplyDelete
  2. Thanks for sharing this blog regarding the best height growth medicine. You can also try here the Height Growth Supplement in the USA.

    ReplyDelete

Post a Comment

Popular posts from this blog

THE POST BALAKOT REVIEW BY LT GEN P R SHANKAR (R)

The Pakistani FM to BBC: War would be suicidal. Pakistan has already started negotiating with a gun to its head! Welcome home Wing Commander Abhinanadan. Well done. You flew into the Valley of Death and survived.  India is proud. Sincere condolences to Air Marshal Waseem Ud Din on the loss of his son Shahaz Ud Din under most unfortunate circumstances. He was incredibly brave to continue his mission when others had turned around.   Paradigm Emerged A lot has happened since Balakot. Some in focus some out. Some hyped. Some diffused. Time to sum up the situation and see where things are heading. Militarily it is called Review of the Situation. I will do it journalistically so that the intellectual western media understands it. They might or not buy our story. Incidentally it is not a story. It is not for sale. This is real live action. Nuclear exchange receding. Not ruled out.     A fundamental paradigm has emerged. India’s fight is against terror. The D

GUNNERS SHOT HITS THE MILLION MARK

IT GIVES ME A GREAT SENSE OF PRIDE THAT ' GUNNERS SHOT ' HAS HAD ITS  'MILLIONTH VIEWER'  TODAY MORNING.  PLEASE SEE THE TABLE BELOW.                                 I STARTED THE BLOG IN MARCH 2019 WHEN SOME OF MY ARTICLES WERE REJECTED BY NATIONAL MEDIA AND REPUTED PLATFORMS. THEY PROBABLY FELT THAT MY  ARTICLES DO NOT DESERVE  SPACE IN THEIR PUBLICATIONS. HOWEVER I THANK THEM FOR NUDGING ME TO STRIKE OUT ON MY OWN.     SO I SET MY OWN STANDARDS.    I ALSO COULD NOT COMPROMISE IN PUTTING ACROSS MY VIEW POINT THE WAY I FELT IT WAS NECESSARY FOR EVERYONE TO KNOW. I CHOSE TO BE UNBIASED AND EXPRESS WHAT IS GOOD FOR INDIA WITHOUT ANY COLOURING.  I HAVE ALSO FELT THAT IT IS IMPORTANT FOR EVERY INDIAN TO KNOW WHAT IS RELEVANT FOR OUR SECURITY IN AS SIMPLE TERMS AS POSSIBLE. IT IS ONLY THEN THAT HE WILL BE ABLE TO APPRECIATE AND SUPPORT THE ARMED FORCES IN THEIR ENDEAVOUR TO PROTECT OUR NATION. OUR MEN AND OFFICERS WHO ARE SERVING ARE THE BEST AND DESERVE OUR GRATITUDE FOR

AGNIPATH : AN INSIDERS VIEW FROM OUTSIDE

As per reports the government is set to finalise the ‘Agnipath’ nee ‘Tour of Duty’ recruitment scheme, under which youth can enlist in the Army for three /five years and be known as ‘Agnivirs’. It is being envisaged that 25% of them would serve for three years and 25% for five years, the remaining 50% would serve for the full term till they reach the retirement age. This major reform is expected to significantly reduce the age profile of the Armed forces. This reform will also result  in significant reduction of pensions. It will curb the ballooning salary and pension bills that are adversely impacting military modernization. Under this arrangement, after completing 3 or 5 years of service, the Army will help the soldier/officer to be recruited in other services. The soldiers would be given a pay-out along with priority in recruitment to certain government jobs, including the central armed police forces. An effort is also on to nudge corporate India into hiring such ex-ToD recruits for