Technical Provisions for Mode S Services and Extended Squitter

DRAFT - Working Paper ASP TSGWP11-01 for review by the TSG during the meeting in June 2011 in Paris
Chapter 2
OVERVIEW OF MODE S SERVICES AND
EXTENDED SQUITTER VERSION 0
2.1 INTRODUCTION
2.1.1 The selective addressing feature of Mode S provides a natural mechanism for a data link. The link design
provides for ground-to-air, air-to-air, air-to-ground, and surface message transfers. Air-to-ground messages may be
either air initiated or ground initiated. The ground initiated message transfer is provided to efficiently read technical
information available on board the aircraft. Mode S also includes certain unique data link capabilities that are referred to
as Mode S services.
2.1.2 Formats and protocols for 1090ES ADS-B messages are also included since registers are defined for each
of these messages so that extended squitter messages can be read out on demand by a ground interrogator, in addition
to being delivered via ADS-B.
2.2 PURPOSE
The purpose of this chapter is to specify detailed technical provisions for the formats and associated protocols for the
following:
a) transponder registers;
b) Mode S specific protocols, including:
i) traffic information broadcast; and
ii) dataflash;
c) Mode S broadcast protocols, including:
i) uplink broadcast;
ii) downlink broadcast; and
d) extended squitter Version 0.
Draft
2.3 EXTENDED SQUITTER VERSION 0
2.3.1 The initial standardization of 1090ES was consistent with RTCA/DO-260 [Ref 43] and was termed 1090ES
Version 0. Using these 1090ES message formats, ADS-B surveillance quality is reported by navigation uncertainty
category (NUC), which can be an indication of either the accuracy or integrity of the navigation data used by ADS-B.
However, there is no indication as to whether the NUC value is based on integrity or accuracy.
2-1
DRAFT - Working Paper ASP TSGWP11-01 for review by the TSG during the meeting in June 2011 in Paris