Lecture 12 (emily)

Question 1

What is the difference between navigation and guidance?

Answer 1

navigation is knowing where you are going and guidance is plotting the path to get you there

Question 2

What is celestial navigation?

Answer 2

using time and angles between local known celestial objects

Question 3

What is Radio navigation?

Answer 3

Using radio frequency sources, i.e GPS

Question 4

What is inertial navigation?

Answer 4

you know your initial position, velocity and attitude, no external references apply

Question 5

How does Instrument Landing system work

Answer 5

• Have something emitting 2 signals and you have to be directly in the middle of the two of them to get the correct version of both of them, guide you along the right path to land. Both horizontally and vertically.

Question 6

What is RADAR?

Answer 6

Measuring how electromagnetic energy bounces cause you know it has constant speed.

Question 7

Why does RADAR need a duplexer

Answer 7

needs to switch quickly between receiving and transmitting so only one receiver is used, if wrong way round waves coming back could hurt receiver.

Question 8

What is primary radar?

Answer 8

Just scanning the sky for anything

Question 9

Why dont we just use primary radar

Answer 9

Required a lot of power to radiate far enough and disturbance might happen due to range

Question 10

What is secondary radar?

Answer 10

sends a signal off, aircraft sends one back and also identifies what is it which primary radar cant do

Question 11

What is Radar cross section?

Answer 11

measures how detectable an object is by radar, area that would if radar beam is sent it would reflect a beam back of the same strength

Question 12

What is the difference between lidar and radar

Answer 12

lidar uses visible/ ultra violet light, way more accurate cause light is higher frequency

Question 13

What are the 3 things that work together to make GPS work?

Answer 13

Satellites- control stations- users

Question 14

Satellites in GPS orbit earth how many times a day

Answer 14

2

Question 15

In GPS how many satellites are in line of site with you at all times

Answer 15

6

Question 16

What do GPS satelites have on board to keep track of time

Answer 16

atomic clock

Question 17

In GPS where do the calculations actually take place?

Answer 17

ground stations

Question 18

in GPS what do end users need to connect [2]

Answer 18

receiver and a clock

Question 19

What are the two modes of GPS?

Answer 19

PPS (precise positioning service) and SPS (standard positioning service)

Question 20

Who mostly uses PPS?

Answer 20

Army and government agency

Question 21

What’s is the difference in accuracy between PPS and SPS

Answer 21

PPS a few cm
SPS 7.8 m

Question 22

What is GLONASS?

Answer 22

Russia’s navigation system
24 active satellites
Each Satellites gives off a different frequency

Question 23

What is Iridium?

Answer 23

constellation of over 70 LEO satellites.

Question 24

What is Iridium used for?

Answer 24

SMS, Internet

Question 25

Why is Iridium better than GPS for some tasks?

Answer 25

requires less power and less delays as the satellites are closer.

Question 26

What is inmarsat?

Answer 26

less satellites - in geostationary

Question 27

Why is Inmarsat better and worse then iridium?

Answer 27

Better as simpler and cheaper
worse as long signal delay and bad coverage at poles