Radar - CFI Commonplace Book

# Key Takeaways - Either primary (radio wave "bounces back" off aircraft) or secondary (using [[transponder]]s) radar - Primary radar has several limitations, which secondary (and later, [[ADS-B]]) has helped address - Either Airport Surveillance Radar ([[ASR]]) or Air Route Surveillance Radar ([[ARSR]]) > [!note] > See [[Weather Radar]] for information on this specific radar application # Details ## Overview | Problem | Solution | Technology Name | | ----------------------------- | ----------------------------------------------------------------------------------------------------- | ------------------------------------------------------------- | | Can't see aircraft visually | Reflect radio energy pulses off metal objects to get distance and direction^[similar to echolocation] | [[#Primary Radar]] | | Unsure who the aircraft is | Install [[transponder]] which listens for *interrogation* and sends a *response* to broadcaster | [[#Secondary Radar/Radar Beacon ( ATCRBS )\|Secondary Radar]] | | Unsure aircraft's altitude | Transponders additionally responds with pressure altitude | [[#Modes\|Mode C]] | | Want more aircraft info | Transponders additionally responds with significantly more information | [[#Mode S]] | | Radar limitations frustrating | Use satellites for position and have all aircraft broadcast their own location and data | [[#ADS-B]] | ## Primary Radar > [!quote] From [[Pilot-Controller Glossary]] > A radar system in which a minute portion of a radio pulse transmitted from a site is reflected by an object and then received back at that site for processing and display at an air traffic control facility. > [!example] By <a href="https://commons.wikimedia.org/wiki/File:Radaroperation.gif">The original uploader was Averse at German Wikipedia.</a>, <a href="https://creativecommons.org/licenses/by-sa/2.0/de/deed.en">CC BY-SA 2.0 DE</a>, via Wikimedia Commons > <img src="https://upload.wikimedia.org/wikipedia/commons/c/c6/Radaroperation.gif"></img> ### Limitations Normally travels in a straight line, but can be bent^[e.g. by [[temperature inversion]]], reflected or attenuated^[e.g. by ground obstacles, precipitation, or heavy clouds], or screened^[by high terrain features]. Historically, screening has been dealt with by installing several radars in strategic locations, but now [[ADS-B]] provides a surveillance solution in areas with challenging terrain. > [!caution]- Wind turbines are a radar problem for non-transponder, non-ADS-B Out aircraft > ![[Figure 4-5-2 Wind Turbine Farm Area of Potential Interference.png]] > From [[AIM 4]], Figure 4-5-2 Finally, tracking primary targets is significantly more workload on [[ATC]]. ## Secondary Radar/Radar Beacon ([[ATCRBS]]) > [!quote] From [[Pilot-Controller Glossary]] > A radar system in which the object to be detected is fitted with cooperative equipment in the form of a radio receiver/transmitter ([[transponder]]). Radar pulses transmitted from the searching transmitter/receiver ([[interrogator]]) site are received in the cooperative equipment and used to trigger a distinctive transmission from the transponder. This reply transmission, rather than a reflected signal, is then received back at the transmitter/receiver site for processing and display at an air traffic control facility. ### Components - **Interrogator**: Scans (in synchronism with the primary radar) and transmits discrete radio signals which repetitiously request all transponders, on the mode being used, to reply. - **Transponder**: Receives the signals from the interrogator and selectively^[only to those interrogations received on the mode to which it is set] replies. These replies are independent of, and much stronger than, a primary radar return. - **Radarscope**: Used by controllers to view returns from both primary and secondary radar. Returns are called **targets**. ### Modes | Mode | Purpose | | ------ | ---------------------------------------------------- | | Mode A | Identification (Squawk code) | | Mode C | Identification (Squawk code) + [[Pressure Altitude]] | ### Mode S Intended to eventually replace [[ATCRBS]], as it allows for individual aircraft interrogation (instead of all aircraft in the radar beam responding). Fully backwards compatible with Modes A or C. ## [[ADS-B]] > [!quote] From [Ins and Outs](https://www.faa.gov/air_traffic/technology/equipadsb/capabilities/ins_outs) by [[FAA]] > ADS-B replaces radar technology with satellites, bringing major advantages. Radar relies on radio signals and antennas to determine an aircraft's location. ADS-B uses satellite signals to track aircraft movements. **Useful Terms** - **ADS-B Out**: *transmission* of ADS-B information from an aircraft - **ADS-B In**: *receipt* of ADS-B information by an aircraft - **ADS-B Ground Stations**: smaller and more adaptable than radar towers and can be placed in locations not possible with radar ### ADS-B Out > [!info] From [Getting to Know Your ADS-B System](https://www.faa.gov/air_traffic/technology/equipadsb/installation/know_adsb_system) by the [[FAA]] > There are approximately 19 pieces of information that your ADS-B is required to transmit through the entire operation > [!attention] ADS-B Out is required in all airspaces defined in [[FAR 91.225 ADS-B Use]] > ![[ADS-B and Mode C Requirements.jpg]] ### ADS-B In Aircraft equipped with ADS-B In can receive the following 3 useful services directly in the flight deck #### 1) Traffic Information Services – Broadcast ([[TIS-B]]) Provides ADS-B Out/In equipped aircraft with surveillance information about aircraft that are not ADS-B equipped^[target must have a transponder and be within radar coverage, though] ![[TIS-B Overview.png]] #### 2) Automatic Dependent Surveillance ‐ Rebroadcast ([[ADS-R]]) Relays ADS-B information transmitted by an aircraft broadcasting on one link (UAT or 1090ES) to aircraft equipped with ADS-B In on the other link. > [!example] > The information for an aircraft equipped with a 1090MHz ADS-B Out system will be re-broadcasted to an aircraft equipped with ADS-B In on the UAT (i.e. 978MHz) frequency, and vice versa. ![[ADS-R Overview.png]] #### 3) Flight Information Services – Broadcast ([[FIS-B]]) Provides the meteorological and aeronautical data to the cockpit, broadcast on UAT frequency^[not on 1090MHz] ![[FIS-B Overview.png]] Some of the currently available FIS-B products are: - Airmen's Meteorological Information ([[AIRMET]]) - Significant Meteorological Information ([[SIGMET]]) - [[Convective SIGMET]] - [[METAR]] - CONUS [[NEXRAD]] - Regional NEXRAD - [[NOTAM]] - [[PIREP]] - Special Use Airspace (SUA) Status - Terminal Aerodrome Forecast ([[TAF]]) - Winds & Temperatures Aloft - [[TIS-B]] Service Status > [!warning] > In flight weather information will have a delay and can not be used for tactical navigation. See [[Time Lapse – Misunderstanding In-Cockpit Weather Displays Can Lead to Tragedy]] # Additional Resources - [[AIM 4]]-5 - [Ins and Outs](https://www.faa.gov/air_traffic/technology/equipadsb/capabilities/ins_outs) by [[FAA]] - [[AC 90-114]] ***Definition*** :: A system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, weather formations, and terrain. ***Additional Info:*** The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging. The term has since entered the English language as a standard word, radar, losing the capitalization in the process. ***Source*** :: [[PHAK Glossary]] ***Meaning*** :: Radio Detection And Ranging #acronym #glossary #concept