MDTS 5734 : Guidance Lecture 5 : Global Positioning Systems. Gerard Leng, MDTS, NUS

Transcription

1 MDTS 5734 : Guidance Lecture 5 : Global Positioning Systems

2 Question : What do we really need for trans-continental navigation? Hint below : It s not GPS!?! First London to Singapore flight by Imperial Airways on 9 December 1933 An 8 day journey with multiple stop overs. Answer :

3 Landmarks may be natural (e.g. coastline ) or artificial (e.g. lighthouse, LORAN ). LORAN - Network of ground based radar stations for LOng Range Navigation prior to Singapore air traffic control centre (ATCC) at 60 Biggin Road, Changi, incorporates a Long Range Radar and Display System LORADS III.

4 Thought experiments Question : How many range measurements from known landmarks do I need to determine my location? Answer : Question : So what happens if we want to determine our location anytime, anywhere on the planet? Answer :

5 Global Positioning System Global Positioning System 24 satellites 6 orbital planes 4 satellites per plane 12 hr, near circular orbit at km

6 1. Why this configuration? 2. How many satellites are needed for a position fix? 3. How is position obtained? 4. What s the catch? 5. So how accurate is the GPS? 6. Is this adequate for precision strike? 7. Are there ways to get more accuracy from the GPS? But after May

7 Pentagon preparing munitions deal to support possible F-15 sale to Singapore WASHINGTON (AFX) - The Pentagon notified the US Congress of plans to sell Singapore up to USD 741 million worth of weapons, equipment and training as part of a proposed sale of F-15 fighters to the republic. The weapons include advanced supersonic air-to-air missiles and satellite-guided bombs.... 'This proposed sale will provide Singapore with a credible self-defense capability that will deter aggression in the region and ensure interoperability with US forces for coalition operations,' the defense agency said. 'Other countries in the region already or will soon possess this capability,' it said. (Adapted from

8 GPS munitions how to convert dumb bombs to smart weapons JDAM Joint Direct Attack Munition JSOW Joint Stand Off Weapon

9 Other GPS systems GLOSNASS Russia GALILEO European Union 北斗 (BEIDOU) China Implications?

10 What are the limitations of GPS? 1. Bad news - GPS signals may be jammed. Commercial GPS jammers are openly available but illegal. FCC FINES CHINESE RETAILER $34.9 MILLION FOR MARKETING ILLEGAL JAMMERS WASHINGTON, May 25, 2016 The Federal Communications Commission today issued a $34.9 million fine against C.T.S. Technology, a Chinese electronics manufacturer and online retailer, for marketing and selling signal jamming devices to U.S. consumers. FC News from the Federal Communications Commission

11 Loss of GPS signal grounded NDP drones A problem with the Global Positioning System of the largestever drone display at the National Day Parade (NDP) Preview 1 last Saturday led to it being cut from the show that night. The skies above the waters at Marina Bay were supposed to light up with seven different formations created by 300 Shooting Star drones, developed by US tech firm Intel. However, a loss of GPS signal that night meant that the drones were unable to take off according to plan. The Straits Times July 27, 2017 Implications?

12 2. Even worse, GPS signals may be spoofed. A small group located off the south coast of Italy successfully took control of an $80 million super-yacht s navigation system using a homemade device,...the work of University of Texas at Austin researchers, led by assistant professor Dr. Todd Humphreys, who were testing out their ability to broadcast counterfeit GPS signals. Digital Trends July 30, 2013 The captain (who agreed to the experiment) had no idea that the boat s GPS system was lying to him not a single alarm bell sounded. Any solution?

13 The return of LORAN? 1. eloran Enchanced LORAN system. A major upgrade of the old LORAN-C systems as a backup for GPS. 2. Signals from ground radar stations are stronger and less easy to jam. The Japan Times 2 May 2016 South Korea, which says it has faced repeated attempts by the rival North to interfere with satellite signals, will award a 15 billion won ($13 million) contract this month to secure technology required to build an alternative landbased radio system called eloran, which it hopes will provide reliable alternative position and timing signals for navigation.