You should establish plans for how to operate as normal for as long as possible during PNT outages. These plans should explicitly detail PNT outages of, for example, one minute, one hour, one day and one month. The exact outage times in the plan need not be these exact arbitrary values, they could relate to very specific capabilities (e.g. oscillator hold over times) but it is important to exercise plans for short, medium, and long outage times spanning minutes to weeks. In some cases an outage as short as one minute may simply result in an action to “do nothing” depending on the exact scenario and system under consideration and in this case it is important to establish and clearly state the shortest time interval for which no action would no longer be acceptable. In some cases the timing interval will not be relative to the moment of the outage, but rather the time until a key independent event specific to your system or your needs. For example, the time remaining until the opening and closing of financial markets, time until the next staffing shift begins, the time until the landing or docking of a large vessel, and so on.

Implement a tiered response strategy that escalates from using backup PNT services to using fully redundant systems based on the severity of the disruption. Integrate automated failover mechanisms where possible to minimise delays in switching between primary and backup systems. Provide clear protocols for manual override and operator decision-making, allowing flexibility in response if automated systems fail or if the nature of the disruption is unexpected.

Your plans should detail acceptable forms of degraded operations which can function with reduced or no PNT data available. For example a degraded mode of operation could be delivery drivers using paper maps stored within their vehicle to navigate instead of using an electronic satellite navigation device if this has failed. In order to understand acceptable levels of degraded performance you will need to first establish the baseline for your nominal performance level. These normal performance parameters can be defined using requirements specifications and existing historical data and they should be metricated and measurable before, during, and after disruptions.

Your plans need to detail under what conditions you would move from a degraded mode of operation to ceasing operations completely until PNT data is available again. While your plans should consider the specific outage times of one minute, one hour, one day and one month, you should also add in any other specific relevant key outage periods or important timing triggers that are specific to your system or your needs, such as the opening and closing of financial markets, shift handovers, weekend operations, and so on.

Where possible, implement integrity checking and cryptographic authentication schemes to aid in the detection of disruptions and to ensure where possible that the integrity level of data is directly calculable.

An example outline sketch of a mitigation plan for a fleet of delivery drivers is given below as an example.

Example mitigation plans for a fleet of delivery drivers serving a supermarket using a company-provided satnav for all navigation, planning, and communication
	Disruption type
Outage period	PNT system has lost power	Communication link lost	Physical damage to PNT system	Poor terrestrial/space weather degrading PNT	PNT device is suffering electronic interference
1 minute	Pull over when safe to verify physical connections	Continue operations and monitor comms link	Use paper maps or a backup system (e.g. personal smartphone)	Be aware of the expected degradation in PNT performance	Wait to see if the interference passes
1 hour	Use paper maps or a backup system (e.g. personal smartphone)	Continue operations and monitor comms link	As above	Be aware of the expected degradation in PNT performance	Look for signs of interference on board the vehicle, e.g. unusual electronics being carried aboard
1 day	Request replacement and use a temporary portable satnav device until repaired	Plan all routes and delivery schedules on paper in advance each day	Replace the PNT system	Be aware of the expected degradation in PNT performance	Request the use of a different vehicle which does not suffer the same interference
1 week	As above	As above and move to alternative communications link	As above	Be aware of the expected degradation in PNT performance	Change journey routes to avoid the interference if it is a regional problem.Use paper maps and alternative PNT sources that do not suffer the interference
1 month	As above	As above	As above	Be aware of the expected degradation in PNT performance	Change journey routes to avoid the interference if it is a regional problem.Use paper maps and alternative PNT sources that do not suffer the interference