Gemini Sustain Plus

On this page, we’re sharing information, useful material and regular updates on the Gemini Sustain Plus programme.

Page contents

    What is Gemini Sustain Plus?

    National Gas Transmission, in partnership with Xoserve and Correla, is undertaking a programme of work to significantly modernise and enhance the Gemini Platform under XRN 5564

    Gemini will continue to provide Capacity and Balancing services, while also delivering system compliance against new Uniform Network Code (UNC) modifications.

    These enhancements will enable change more efficiently, while also driving an improved customer experience.

    Overview of scope

    These activities will include: 

    • Converting all current Gemini functionality and code into modern (Java microservices) code
    • Delivering new and existing functional requirements, and new non-functional requirements
    • Consolidating and redesigning the Gemini user interface screens
    • Implementing Azure cloud infrastructure components (including replacing the current Oracle database)
    • Improvements to the support service arrangement to respond better to incidents and change (in-line with new service levels and KPIs)


    The Gemini Sustain Plus programme will be delivered over a two-year period.

    The target delivery is currently planned for September 2024.


    Project news - Action required

    Connectivity and onboarding – 1 April to 31 July

    This phase is mandatory for all Gemini users. Any users who don’t participate in this stage will be unable to carry out any Gemini processes when the new system launches.

    You must engage with the Gemini user audit as soon as possible. If you need further information please email urgently.

    Market trials – 3 June to 12 July

    During this period you’ll have the chance to familiarise yourself with the new system before it launches.

    We highly recommend you take this opportunity to understand the new screens and features these updates will deliver.

    Please register for market trials no later than 13 May 2024.

    Register now


    Focus groups

    National Gas have launched a series of Gemini Sustain Plus focus groups.

    The next focus group session will be held virtually via Microsoft Teams on 18 March 2024 from 1 - 3pm.

    This will be an informative session and an opportunity to meet the teams from National Gas and their delivery partners Xoserve, Correla and Wipro.

    If you wish to attend and haven't received the Teams invite please email

    Email us

    Customer focus groups schedule

    View the dates, times and access material for our customer focus groups below:

    Date Time More information
    18 March 2024 1pm - 3pm TBC


    Date Time Meeting information
    25 September 2023 1pm - 3pm

    Focus Group presentation

    GS+ demo video

    Focus Group Q&A

    20 November 2023 1pm - 3pm

    Focus Group presentation

    GS+ demo video 2

    Focus Group Q&A

    22 January 2024 1pm - 3pm

    Focus Group presentation

    GS+ demo video 3

    GS+ training video

    Focus Group Q&A



    Common queries

    Gemini Sustain Plus is intended to have no impact to the existing Gemini incoming and outgoing interfaces to the Industry. Some new API interfaces will be made available for use.

    Opportunity for training will be provided in 2024 (dates to TBC). It is essential for all companies that use Gemini to participate.

    Yes, this will take place Q2, 2024 and it is essential for all companies that use Gemini to participate. Details and invitations will be issued later in 2023.

    There will be some functional changes which are in response to pain points raised by customers. i.e. the look and feel of the system, as well as bringing together Entry and Exit Capacity.

    Currently, go-live is scheduled for September 2024.

    Updates will be given to the DSC Change Management Committee (ChMC), the Transmission Workgroup and updates will be published on our dedicated Gemini Sustain Plus webpage.

    No, after implementation of the Sustain Plus programme Citrix will no longer be required to access Gemini. Portal access will be available using a web browser over an internet connection.

    No, a new identity management solution is being implemented as part of Gemini Sustain Plus – this will require the creation of new access credentials for all system users.

    The existing Gemini API functionality will continue, but there will be changes to the connectivity and user credentials. Any changes to the technical specifications will be published to the industry.

    There will be additional download functionality (xml) incorporated into the new system design.

    No, there won't be any parallel system operation, but there will be an on-boarding period which will include Market Trials. This will allow users to test connectivity, access the updated user interface and new functionality. Training will be available in advance of go-live.

    The Gemini ‘Change Freeze’ period is aligned to the Implementation Dress Rehearsal phase of the Gemini Sustain Plus programme. This ensures there is a confirmed code base on which to undertake the dress rehearsal activities. It also helps mitigate the risk of inefficient spend.

    If the Sustain Plus implementation date changes, the change freeze will be realigned to the updated implementation dress rehearsal period.

    Information on this change would be provided at all standard industry forums, along with bespoke programme communications for maximum transparency.

    Get in touch

    If you have any questions or queries about Gemini Sustain Plus, please email us at

    Email us

    Report an issue

    If you encounter any issues with Gemini, please raise a support request with our Service Desk.

    Raise a support request

    Register your interest in market trials

    If you’d like to take part in our market trials phase, please complete the following form.

    Register here

    Need help?

    Please raise a support request if you have any queries regarding Gemini.

    Raise a support request

    Focus groups

    National Gas have launched a series of Gemini Sustain Plus focus groups.

    The next session will be on Microsoft Teams on 18 March 2024.

    If you wish to attend and haven’t received the Teams invite please email us.

    Email us