Asterix category 021 - ADS-B Target Reports

category: 021

edition: 2.5

date: 2021-02-18

Preamble

Surveillance data exchange. ADS-B Target Reports.

Description of standard data items

I021/008 - Aircraft Operational Status

Definition: Identification of the operational services available in the aircraft while airborne.

Structure:

I021/008/RA - TCAS Resolution Advisory Active

I021/008/TC - Target Trajectory Change Report Capability

I021/008/TS - Target State Report Capability

I021/008/ARV - Air-Referenced Velocity Report Capability

I021/008/CDTIA - Cockpit Display of Traffic Information Airborne

I021/008/NOTTCAS - TCAS System Status

I021/008/SA - Single Antenna

Note:
  • Additional Aircraft Status Information is available in the Reserved Expansion Field of Category 021.

I021/010 - Data Source Identification

Definition: Identification of the ADS-B station providing information.

Structure:

I021/010/SAC - System Area Code

I021/010/SIC - System Identification Code

Note:

I021/015 - Service Identification

Definition: Identification of the service provided to one or more users.

Structure:

Notes:

  1. The service identification is allocated by the system.
  2. The service identification is also available in item I023/015 [Ref. 3].

I021/016 - Service Management

Definition: Identification of services offered by a ground station (identified by a SIC code).

Structure:

Notes:

  1. This item contains the same information as item I023/101 in ASTERIX category 023 [Ref. 3]. Since not all service users receive category 023 data, this information has to be conveyed in category 021 as well.
  2. If this item is due to be sent according to the encoding rule above, it shall be sent with the next target report

I021/020 - Emitter Category

Definition: Characteristics of the originating ADS-B unit.

Structure:

I021/040 - Target Report Descriptor

Definition: Type and characteristics of the data as transmitted by a system.

Structure:

Extended item.

I021/040/ATP - Address Type

I021/040/ARC - Altitude Reporting Capability

I021/040/RC - Range Check

I021/040/RAB - Report Type

(FX)

I021/040/DCR - Differential Correction

I021/040/GBS - Ground Bit Setting

I021/040/SIM - Simulated Target

I021/040/TST - Test Target

I021/040/SAA - Selected Altitude Available

I021/040/CL - Confidence Level

(FX)

I021/040/(spare)

I021/040/LLC - List Lookup Check

I021/040/IPC - Independent Position Check

I021/040/NOGO - No-go Bit Status

I021/040/CPR - Compact Position Reporting

I021/040/LDPJ - Local Decoding Position Jump

I021/040/RCF - Range Check

(FX)

Notes:

  1. Bit 3 indicates that the position reported by the target is within a credible range from the ground station. The range check is followed by the CPR validation to ensure that global and local position decoding both indicate valid position information. Bit 3=1 indicates that the range check was done, but the CPR validation is not yet completed. Once CPR validation is completed, Bit 3 will be reset to 0.

  2. Bits 8/6 (ATP): values 0, 2 and 3 depend on the value of the Control Field (CF) in the Downlink Format 18 Message as defined in the ADS-B MOPS (EUROCAE ED-102/RTCA DO-260, Ref [11] Table 2-7).

    CF=0 denotes a 24-bit ICAO address and shall be encoded with ATP=0.

    CF=1 denotes “another kind of address for the transmitting ADS-B participant: a self assigned “anonymous” address, a ground vehicle address, or a surface obstruction address”.

    Thus, from the downlinked information it is not possible to distinguish between a “Surface Vehicle Address – ATP=2” or an “Anonymous Address – ATP=3”.

    Therefore how CF=1 in the received 1090 MHz Extended Squitter is encoded in ATP shall be described in the ICD of the ASTERIX system.

    It should be noted, however, that EUROCAE Document ED-129B (the “Technical Specification for a 1090MHz Extended Squitter ADS-B Ground System”, Ref. [12]) requires ATP to be set to “3” if CF=1. Therefore it is recommended that a value of CF=1 received in the Extended Squitter should be encoded as ATP=3.

  3. Except for Bit 5 (NOGO), the second extension signals the reasons for which the report has been indicated as suspect (indication Confidence Level (CL) in the first extension).

  4. Bit 7, if set to 1, indicates that a lookup in a Black-list/White-list identified that the target may be suspect.

  5. Bit 6, if set to 1, indicates that the position reported by the target was validated by an independent means and a discrepancy was detected. If no independent position check is implemented, the default value “0” is to be used.

  6. Bit 5 represents the setting of the GO/NOGO-bit as defined in item I023/100 of Category 023 [Ref. 2].

  7. Bit 2 indicates that the Range Check failed, i.e. the target is reported outside the credible range for the Ground Station. For operational users such a target will be suppressed. In services used for monitoring the Ground Station, the target will be transmitted with bit 2 indicating the fault condition.

I021/070 - Mode 3/A Code in Octal Representation

Definition: Mode-3/A code converted into octal representation.

Structure:

I021/070/(spare)

I021/070/MODE3A - Mode-3/A Reply in Octal Representation

I021/071 - Time of Applicability for Position

Definition: Time of applicability of the reported position, in the form of elapsed time since last midnight, expressed as UTC.

Structure:

Notes:

  1. The time of applicability value is reset to zero at every midnight.
  2. The time of applicability indicates the exact time at which the position transmitted in the target report is valid.

I021/072 - Time of Applicability for Velocity

Definition: Time of applicability (measurement) of the reported velocity, in the form of elapsed time since last midnight, expressed as UTC.

Structure:

Notes:

  1. The time of the applicability value is reset to zero at every midnight.
  2. The time of applicability indicates the exact time at which the velocity information transmitted in the target report is valid.
  3. This item will not be available in some ADS-B technologies.

I021/073 - Time of Message Reception for Position

Definition: Time of reception of the latest position squitter in the Ground Station, in the form of elapsed time since last midnight, expressed as UTC.

Structure:

Note:
  • The time of message reception value is reset to zero at every midnight.

I021/074 - Time of Message Reception of Position-High Precision

Definition: Time at which the latest ADS-B position information was received by the ground station, expressed as fraction of the second of the UTC Time.

Structure:

I021/074/FSI - Full Second Indication

I021/074/TOMRP - Fractional Part of the Time of Message Reception for Position in the Ground Station

I021/075 - Time of Message Reception for Velocity

Definition: Time of reception of the latest velocity squitter in the Ground Station, in the form of elapsed time since last midnight, expressed as UTC.

Structure:

Note:
  • The time of message reception value is reset to zero at every midnight.

I021/076 - Time of Message Reception of Velocity-High Precision

Definition: Time at which the latest ADS-B velocity information was received by the ground station, expressed as fraction of the second of the UTC Time.

Structure:

I021/076/FSI - Full Second Indication

I021/076/TOMRP - Fractional Part of the Time of Message Reception for Position in the Ground Station

I021/077 - Time of ASTERIX Report Transmission

Definition: Time of the transmission of the ASTERIX category 021 report in the form of elapsed time since last midnight, expressed as UTC.

Structure:

Note:
  • The time of ASTERIX report transmission value is reset to zero at every midnight.

I021/080 - Target Address

Definition: Target address (emitter identifier) assigned uniquely to each target.

Structure:

Note:

I021/090 - Quality Indicators

Definition: ADS-B quality indicators transmitted by a/c according to MOPS version.

Structure:

Extended item.

I021/090/NUCRNACV - Navigation Uncertainty Category for Velocity NUCr or the Navigation Accuracy Category for Velocity NACv

I021/090/NUCPNIC - Navigation Uncertainty Category for Position NUCp or Navigation Integrity Category NIC

(FX)

I021/090/NICBARO - Navigation Integrity Category for Barometric Altitude

I021/090/SIL - Surveillance (version 1) or Source (version 2) Integrity Level

I021/090/NACP - Navigation Accuracy Category for Position

(FX)

I021/090/(spare)

I021/090/SILS - SIL-Supplement

I021/090/SDA - Horizontal Position System Design Assurance Level (as Defined in Version 2)

I021/090/GVA - Geometric Altitude Accuracy

(FX)

I021/090/PIC - Position Integrity Category

I021/090/(spare)

(FX)

Notes:

  1. Apart from the “PIC” item, all items are defined as per the respective link technology protocol version (“MOPS version”, see I021/210).
  2. The primary subfield is kept for backwards compatibility reasons. Version 2 NIC-values shall be mapped accordingly. This is required to ensure that downstream systems, which are not capable of interpreting extensions 2 and 3 (because they use an ASTERIX edition earlier than 2.0) still get the required information
  3. “Version 1” or “Version 2” refers to the MOPS version as defined in data item I021/210, bits 6/4
  4. “Version 2” refers to the MOPS version as defined in data item I021/210, bits 6/4
  5. PIC=0 is defined for completeness only. In this case the third extension shall not be generated.
  6. For ED102A/DO260B PIC values of 7 and 9, the NIC supplements for airborne messages (NIC supplements A/B) and surface messages (NIC supplements A/C) are listed. For ED102A/DO260B PIC=8, the NIC supplements A/B for airborne messages are listed. For DO260A PIC values of 7 and 8, the NIC supplement for airborne messages is shown in brackets. The aircraft air-ground status, and hence message type (airborne or surface), is derived from the GBS-bit in I021/040, 1 st extension.

I021/110 - Trajectory Intent

Definition: Reports indicating the 4D intended trajectory of the aircraft.

Structure:

Compound item (FX)

I021/110/TIS - Trajectory Intent Status

Extended item.

I021/110/TIS/NAV

  • 1 bit [.]

  • values:

    0: Trajectory Intent Data is available for this aircraft
    1: Trajectory Intent Data is not available for this aircraft

I021/110/TIS/NVB

  • 1 bit [.]

  • values:

    0: Trajectory Intent Data is valid
    1: Trajectory Intent Data is not valid

I021/110/TIS/(spare)

  • 5 bits [.....]

(FX)

  • extension bit

    0: End of data item
    1: Extension into next extent

I021/110/TID - Trajectory Intent Data

Repetitive item, repetition factor 8 bits.

I021/110/TID/TCA

  • 1 bit [.]

  • values:

    0: TCP number available
    1: TCP number not available

I021/110/TID/NC

  • 1 bit [.]

  • values:

    0: TCP compliance
    1: TCP non-compliance

I021/110/TID/TCPN

Trajectory Change Point number

  • 6 bits [......]
  • raw value

I021/110/TID/ALT - Altitude in Two’s Complement Form

  • 16 bits [................]
  • signed quantity
  • unit: “ft”
  • LSB = 10 ft
  • value  >  =  − 1500 ft
  • value  <  = 150000 ft

I021/110/TID/LAT - In WGS.84 in Two’s Complement

  • 24 bits [........................]
  • signed quantity
  • unit: “°”
  • LSB = 180/223 °  ≈ 2.15e − 5 °
  • value  >  =  − 90 °
  • value  <  = 90 °

I021/110/TID/LON - In WGS.84 in Two’s Complement

  • 24 bits [........................]
  • signed quantity
  • unit: “°”
  • LSB = 180/223 °  ≈ 2.15e − 5 °
  • value  >  =  − 180 °
  • value  < 180 °

I021/110/TID/PT - Point Type

  • 4 bits [....]

  • values:

    0: Unknown
    1: Fly by waypoint (LT)
    2: Fly over waypoint (LT)
    3: Hold pattern (LT)
    4: Procedure hold (LT)
    5: Procedure turn (LT)
    6: RF leg (LT)
    7: Top of climb (VT)
    8: Top of descent (VT)
    9: Start of level (VT)
    10: Cross-over altitude (VT)
    11: Transition altitude (VT)

I021/110/TID/TD

  • 2 bits [..]

  • values:

    0: N/A
    1: Turn right
    2: Turn left
    3: No turn

I021/110/TID/TRA

Turn Radius Availability

  • 1 bit [.]

  • values:

    0: TTR not available
    1: TTR available

I021/110/TID/TOA

  • 1 bit [.]

  • values:

    0: TOV available
    1: TOV not available

I021/110/TID/TOV - Time Over Point

  • 24 bits [........................]
  • unsigned quantity
  • unit: “s”
  • LSB = 1 s

I021/110/TID/TTR - TCP Turn Radius

  • 16 bits [................]
  • unsigned quantity
  • unit: “NM”
  • LSB = 1/100 NM  ≈ 1.00e − 2 NM
  • value  >  = 0 NM
  • value  <  = 13107/20 NM

Notes:

  1. NC is set to one when the aircraft will not fly the path described by the TCP data.
  2. TCP numbers start from zero.
  3. LT = Lateral Type
  4. VT = Vertical Type
  5. TOV gives the estimated time before reaching the point. It is defined as the absolute time from midnight.
  6. TOV is meaningful only if TOA is set to 1.

I021/130 - Position in WGS-84 Co-ordinates

Definition: Position in WGS-84 Co-ordinates.

Structure:

I021/130/LAT - Latitude

I021/130/LON - Longitude

Notes:

I021/131 - High-Resolution Position in WGS-84 Co-ordinates

Definition: Position in WGS-84 Co-ordinates in high resolution.

Structure:

I021/131/LAT - Latitude

I021/131/LON - Longitude

Notes:

I021/132 - Message Amplitude

Definition: Amplitude, in dBm, of ADS-B messages received by the ground station, coded in two’s complement.

Structure:

Note:
  • The value gives the amplitude of the latest received squitter.

I021/140 - Geometric Height

Definition: Minimum height from a plane tangent to the earth’s ellipsoid, defined by WGS-84, in two’s complement form.

Structure:

Note:
  1. LSB is required to be less than 10 ft by ICAO.
  2. A value of ‘0111111111111111’ indicates that the aircraft transmits a “greater than” indication.

I021/145 - Flight Level

Definition: Flight Level from barometric measurements,not QNH corrected, in two’s complement form.

Structure:

I021/146 - Selected Altitude

Definition: The Selected Altitude as provided by the avionics and corresponding either to the MCP/FCU Selected Altitude (the ATC cleared altitude entered by the flight crew into the avionics) or to the FMS Selected Altitude.

Structure:

I021/146/SAS - Source Availability

I021/146/S - Source

I021/146/ALT - Altitude

Notes:

  1. The Selected Altitude provided in this field is not necessarily the “Target Altitude” as defined by ICAO.
  2. The value of “Source” (bits 15/14) indicating “unknown” or “Aircraft Altitude” is kept for backward compatibility as these indications are not provided by “version 2” systems as defined by data item I021/210, bits 6/4.
  3. Vertical mode indications supporting the determination of the nature of the Selected Altitude are provided in the Reserved Expansion Field in the subfield NAV.

I021/148 - Final State Selected Altitude

Definition: The vertical intent value that corresponds with the ATC cleared altitude, as derived from the Altitude Control Panel (MCP/FCU).

Structure:

I021/148/MV - Manage Vertical Mode

I021/148/AH - Altitude Hold Mode

I021/148/AM - Approach Mode

I021/148/ALT - Altitude

Notes:

I021/150 - Air Speed

Definition: Calculated Air Speed (Element of Air Vector).

Structure:

I021/150/IM

I021/150/AS - Air Speed (IAS or Mach)

I021/151 - True Airspeed

Definition: True Air Speed.

Structure:

I021/151/RE - Range Exceeded Indicator

I021/151/TAS - True Air Speed

Notes:

I021/152 - Magnetic Heading

Definition: Magnetic Heading (Element of Air Vector).

Structure:

Notes:

I021/155 - Barometric Vertical Rate

Definition: Barometric Vertical Rate, in two’s complement form.

Structure:

I021/155/RE - Range Exceeded Indicator

I021/155/BVR - Barometric Vertical Rate

Notes:

I021/157 - Geometric Vertical Rate

Definition: Geometric Vertical Rate, in two’s complement form, with reference to WGS-84.

Structure:

I021/157/RE - Range Exceeded Indicator

I021/157/GVR - Geometric Vertical Rate

Notes:

I021/160 - Airborne Ground Vector

Definition: Ground Speed and Track Angle elements of Airborne Ground Vector.

Structure:

I021/160/RE - Range Exceeded Indicator

I021/160/GS - Ground Speed Referenced to WGS-84

I021/160/TA - Track Angle Clockwise Reference to True North

Notes:

  1. The RE-Bit, if set, indicates that the value to be transmitted is beyond the range defined for this specific data item and the applied technology. In this case the Ground Speed contains the maximum value that can be downloaded from the aircraft avionics and the RE-bit indicates that the actual value is greater than the value contained in the field.
  2. The Surface Ground Vector format is defined in the Reserved Expansion Field in the subfield SGV.

I021/161 - Track Number

Definition: An integer value representing a unique reference to a track record within a particular track file.

Structure:

I021/161/(spare)

I021/161/TRNUM - Track Number

I021/165 - Track Angle Rate

Definition: Rate of Turn, in two’s complement form.

Structure:

I021/165/(spare)

I021/165/TAR - Track Angle Rate

Notes:

  1. A positive value represents a right turn, whereas a negative value represents a left turn.
  2. Maximum value means Maximum value or above.
  3. This item will not be transmitted for the technology 1090 MHz Extended Squitter.

I021/170 - Target Identification

Definition: Target (aircraft or vehicle) identification in 8 characters, as reported by the target.

Structure:

I021/200 - Target Status

Definition: Status of the target

Structure:

I021/200/ICF - Intent Change Flag (see Note)

I021/200/LNAV - LNAV Mode

I021/200/ME - Military Emergency

I021/200/PS - Priority Status

I021/200/SS - Surveillance Status

Notes:

I021/210 - MOPS Version

Definition: Identification of the MOPS version used by a/c to supply ADS-B information.

Structure:

I021/210/(spare)

I021/210/VNS - Version Not Supported

I021/210/VN - Version Number

I021/210/LTT - Link Technology Type

Notes:

I021/220 - Met Information

Definition: Meteorological information.

Structure:

Compound item (FX)

I021/220/WS - Wind Speed

I021/220/WD - Wind Direction

I021/220/TMP - Temperature

I021/220/TRB - Turbulence

I021/230 - Roll Angle

Definition: The roll angle, in two’s complement form, of an aircraft executing a turn.

Structure:

Notes:

  1. Negative Value indicates “Left Wing Down”.
  2. Resolution provided by the technology “1090 MHz Extended Squitter” is 1 degree.

I021/250 - Mode S MB Data

Definition: Mode S Comm B data as extracted from the aircraft transponder.

Structure:

Repetitive item, repetition factor 8 bits.

Notes:

  1. For the transmission of BDS20, item 170 should be used.
  2. For the transmission of BDS30, item 260 is used.

I021/260 - ACAS Resolution Advisory Report

Definition: Currently active Resolution Advisory (RA), if any, generated by the ACAS associated with the transponder transmitting the RA message and threat identity data.

Structure:

I021/260/TYP - Message Type (= 28 for 1090 ES, Version 2)

I021/260/STYP - Message Sub-type (= 2 for 1090 ES, Version 2)

I021/260/ARA - Active Resolution Advisories

I021/260/RAC - RAC (RA Complement) Record

I021/260/RAT - RA Terminated

I021/260/MTE - Multiple Threat Encounter

I021/260/TTI - Threat Type Indicator

I021/260/TID - Threat Identity Data

Notes:

  1. Version denotes the MOPS version as defined in I021/210, bits 6/4
  2. This data items copies the value of BDS register 6,1 for message type 28, subtype 2
  3. The “TYP” and “STYP” items are implementation (i.e. link technology) dependent.
  4. Refer to ICAO Annex 10 SARPs for detailed explanations [Ref. 5]

I021/271 - Surface Capabilities and Characteristics

Definition: Operational capabilities of the aircraft while on the ground.

Structure:

Extended item.

I021/271/(spare)

I021/271/POA - Position Offset Applied

I021/271/CDTIS - Cockpit Display of Traffic Information Surface

I021/271/B2LOW - Class B2 Transmit Power Less Than 70 Watts

I021/271/RAS - Receiving ATC Services

I021/271/IDENT - Setting of IDENT Switch

(FX)

I021/271/LW - Length and Width of the Aircraft

I021/271/(spare)

(FX)

Notes:

  1. Version 2 (as defined in I021/210, bits 6/4) data technology protocols encode “No Data or Unknown” with value 0. In this case data item I021/271, first extension is not generated.
  2. As of edition 2.2 the structure of this data item has been changed. Edition 2.2 is not backwards compatible with previous editions.

I021/295 - Data Ages

Definition: Ages of the data provided.

Structure:

Compound item (FX)

I021/295/AOS - Aircraft Operational Status Age

Age of the information transmitted in item I021/008.

I021/295/TRD - Target Report Descriptor Age

Age of the Target Report Descriptor, item I021/040

I021/295/M3A - Mode 3/A Age

Age of the Mode 3/A Code, item I021/070

I021/295/QI - Quality Indicators Age

Age of the Quality Indicators, item I021/090

I021/295/TI1 - Trajectory Intent Age

Age of the Trajectory Intent information, item I021/110

I021/295/MAM - Message Amplitude Age

Age of the message amplitude, item I021/132

I021/295/GH - Geometric Height Age

Age of the Geometric Height, item 021/140

I021/295/FL - Flight Level Age

Age of the Flight Level, item I021/145

I021/295/ISA - Intermediate State Selected Altitude Age

Age of the Intermediate State Selected Altitude, item I021/146

I021/295/FSA - Final State Selected Altitude Age

Age of the Final State Selected Altitude, item I021/148

I021/295/AS - Air Speed Age

Age of the Air Speed, item I021/150

I021/295/TAS - True Air Speed Age

Age of the True Air Speed, item I021/151

I021/295/MH - Magnetic Heading Age

Age of the Magnetic Heading, item I021/152

I021/295/BVR - Barometric Vertical Rate Age

Age of the Barometric Vertical Rate, item I021/155

I021/295/GVR - Geometric Vertical Rate Age

Age of the Geometric Vertical Rate, item I021/157

I021/295/GV - Ground Vector Age

Age of the Ground Vector, item I021/160

I021/295/TAR - Track Angle Rate Age

Age of the Track Angle Rate, item I021/165

I021/295/TI2 - Target Identification Age

Age of the Target Identification, item I021/170

I021/295/TS - Target Status Age

Age of the Target Status, item I021/200

I021/295/MET - Met Information Age

Age of the Meteorological Information, item I021/220

I021/295/ROA - Roll Angle Age

Age of the Roll Angle, item I021/230

I021/295/ARA - ACAS Resolution Advisory Age

Age of the latest update of an active ACAS Resolution Advisory, item I021/260

I021/295/SCC - Surface Capabilities and Characteristics Age

Age of the information on the surface capabilities and characteristics of the respective target, item I021/271

Notes:

I021/400 - Receiver ID

Definition: Designator of Ground Station in Distributed System.

Structure:

I021/RE - Reserved Expansion Field

Definition: Expansion

Structure:

Explicit item (RE)

I021/SP - Special Purpose Field

Definition: Special Purpose Field

Structure:

Explicit item (SP)

User Application Profile for Category 021