Outer Space
Individual constellation contributions to multi-GNSS space service volume
To convey a consistent set of capabilities across all GNSS constellations an SSV capabilities template has been completed by each GNSS service provider to capture their contributions to each of the parameters identified in section 3.2. The full text of these completed templates along with appropriate context is available in annex A. This chapter presents an aggregated subset of the full data so that the individual SSV characteristics of each constellation can be readily compared and contrasted.
Potential future evolutions of this space service volume booklet
To promote the use of multi-GNSS for the purpose of safe robotic and/or crewed missions in the space service volume as defined in this booklet and beyond including cislunar space it will be necessary to update this booklet to extend efforts on simulation and modelling and elaborate further on recommendations for GNSS providers.
Executive summary
Global navigation satellite systems (GNSS) which were originally designed to provide positioning velocity and timing services for terrestrial users are now also being increasingly utilized for autonomous navigation in space. Historically most space users have been located at low altitudes where GNSS signal reception is similar to that on the ground. More recently however users are relying on these signals at high altitudes near to or above the GNSS constellations themselves.
Description of individual GNSS support to space service volume
The Global Positioning System (GPS) is a United States-owned utility that provides users with positioning navigation and timing (PNT) services. GPS represents a “system of systems” consisting of three segments: a space segment employing a nominal constellation of 24 space vehicles (SV) transmitting one-way signals with the GPS satellite’s position and time; a control segment consisting of a global network of ground facilities that track the GPS satellites monitor their transmissions perform analyses and send commands and data to the constellation;
Acknowledgements
A very special thank you to the United Nations Office for Outer Space Affairs (UNOOSA) for its invaluable work in promoting international cooperation in the peaceful uses and exploration of space and in helping ICG to build a multi-GNSS environment for sustainable development. In particular we would like to thank Simonetta Di Pippo Director of UNOOSA for the full cooperation received and Sharafat Gadimova of the ICG Executive Secretariat for her dedicated work and support.
Detailed simulation configuration and results
This chapter provides the full set of SSV simulation results as well as the configuration and methodology used to execute the simulations themselves. This information should allow the simulations to be independently implemented and the results to be independently reproduced.
Simulated performance of interoperable space service volume
The Working Group B (WG-B) of the International Committee on Global Navigation Satellite Systems (ICG) through its Space Use Subgroup has simulated the GNSS single- and multipleconstellation performance expectations in SSV based on the individual constellation signal characteristics documented in chapter 4. As outlined in chapter 3 navigation performance in SSV is primarily characterized by three properties: user range error (URE) received signal power and signal availability. The focus of these simulations is on signal availability and geometry which serve as proxies for navigation capability.
Recommendations
The recommendations in this annex were adopted by the International Committee on GNSS (ICG) via Working Group B (WG-B) to advance development and adoption of the interoperable GNSS space service volume by providers users and equipment manufacturers.
Constellation specification for simulations
This annex provides the orbital parameters used for every constellation for the SSV simulations reported in this booklet. These parameters are defined at the simulation start epoch 1 January 2016 12:00:00 UTC.
The Interoperable Global Navigation Satellite Systems Space Service Volume - Second Edition
Global navigation satellite systems (GNSS) which were originally designed to provide positioning velocity and timing services for terrestrial users are now increasingly utilized for autonomous navigation in space as well. Historically most space users have been located at low altitudes where GNSS signal reception is similar to that on the ground. More recently however users are relying on these signals at high altitudes near to or above the GNSS constellations themselves. The availability and performance of GNSS signals at high altitude is documented as the GNSS Space Service Volume (SSV). While different definitions of the SSV exist and may continue to exist for the different service providers within the context of this booklet it is defined as the region of space between 3000 km and 36000 km above the Earth’s surface which is the geostationary altitude. For space users located at low altitudes (below 3000 km) the GNSS signal reception is similar to that for terrestrial users and can be conservatively derived from the results presented for the lower SSV in this booklet.
Interoperable GNSS space service volume
Historically most space users have been located at low altitudes where GNSS signal reception is similar to that on the ground. More recently however users are relying on these signals at high altitudes near to or above the GNSS constellations themselves. The availability and performance of GNSS signals at high altitude is documented as the GNSS SSV. While different definitions of SSV exist and may continue to exist for the different service providers within the context of this booklet it is defined as the region of space between 3000 km and 36000 km above the Earth’s surface which is the geostationary altitude. For space users located at low altitudes (below 3000 km) GNSS signal reception is similar to that for terrestrial users and can be conservatively derived from the results presented for the lower SSV in this booklet.
Flight experiences
Real-world examples of space missions employing GNSS in the space service volume (SSV) enable future GNSS space users to understand the full scope of achievable benefits and on-orbit performance expectations in this environment. The profiles in this section were solicited from GNSS provider teams and spacecraft mission developers to share relevant historical on-orbit and near-future mission experiences and analysis. Specific information requested includes the mission description and purpose GNSS receivers employed performance benefits resulting from using GNSS in SSV and details of observed or predicted on-orbit performance. These profiles describe the on-orbit capability of interoperable GNSS space use and use of GNSS in SSV beyond the documented characteristics of each constellation described in annex A.
Resources
IS-GPS-200: Defines the requirements related to the interface between the GPS space and user segments for radio frequency L1 (L1 C/A) and L2 (L2C).
Benefits to users
The number and scope of GNSS-based space applications has grown significantly since the first GNSS space receiver was flown. The vast majority of space users are operating in low Earth orbit (LEO) where use of GNSS receivers has become routine. For spacecraft in SSV however the first demonstrated uses came in the late 1990s.
Introduction
The vast majority of Global Navigation Satellite System (GNSS) users are located on the ground and the GNSS systems are designed to serve these users. However the number of satellites utilizing on-board GNSS space receivers is steadily growing. Space receivers in SSV operate in an environment significantly different than the environment of a classical terrestrial receiver or GNSS receiver in low Earth orbit (LEO).
Conclusions and recommendations
GNSS which were originally designed to provide positioning and timing services to users on the ground are increasingly being utilized for on-board autonomous navigation in space. While use of GNSS in LEO has become routine its use in higher orbits has historically posed unique and difficult challenges including limited geometric visibility and reduced signal strength. Only recently have these been overcome by high-altitude users through weak-signal processing techniques and on-board estimation filters.
Évaluation des dommages sur les sites du patrimoine mondial par l’UNOSAT
Depuis 20 ans l’UNOSAT développe son expertise dans l’utilisation des technologies de l’information géospatiale afin de promouvoir la prise de décision reposant sur des données probantes en faveur de la paix la sécurité et la résilience. Créé en 2001 en tant que programme opérationnel de l’Institut des Nations Unies pour la formation et la recherche (UNITAR) l’UNOSAT a pour mission de soutenir les États membres les agences des Nations Unies les ONG et les organisations internationales. Il fournit des analyses géospatiales coordonnées et développe les capacités en matière de technologies de la géo-information afin de favoriser la réalisation des objectifs de développement durable (ODD). Il s’agit notamment de documenter et de sensibiliser à l’impact dévastateur que les dangers et les conflits peuvent avoir sur notre patrimoine mondial et de montrer comment les technologies et les données d’information géospatiale peuvent soutenir les efforts de préservation des sites culturels et naturels.
Órganos consultivos
Desde que el ser humano sintió la necesidad de observar lo que ocurría en el entorno que le rodeaba se consideró útil un punto de vista más elevado. Los árboles las colinas y las montañas sirvieron para este propósito hasta que los humanos fueron capaces de “volar”. Los globos los aviones y más tarde los satélites ofrecían plataformas de observación que permitían una percepción más general y completa de la superficie terrestre. La necesidad de una visión de este tipo estuvo motivada inicialmente por fines militares pero otras aplicaciones también han aprovechado mucho dichas posibilidades.
Close-Up: UNOSAT reveals damage to Syria’s cultural heritage
An upcoming UNESCO-UNITAR publication – Ten years of conflict the state of cultural heritage in Syria – will assess through satellite images the destruction the Syrian conflict has inflicted to date on the country’s cultural heritage.