Guidelines for interruptions in radar operations
EISCAT in support of rocket launched experiments
The PI of a 1st priority experiment may relinquish their experiment time for a rocket launch, but they are not obliged to do so. EISCAT encourages collaboration and discussion between all parties running parallel experimental campaigns during rocket launches as early as possible and will make amendments to the schedule if all parties are agreed. For further information regarding scheduling and rocket launch procedures please read the following:
EISCAT rules of the road for rocket campaigns,
a users guide how to plan for rocket campaigns
EISCAT has a long and happy history of supporting experiments carried on rockets; the radar data can provide a powerful complement to in-situ measurements.
The team behind the rocket experiment can get access to EISCAT observation time through their own Special Programme (SP) time if they are an Associate or Affiliate, or by collaborating with scientists who are. Alternatively they can apply to the Peer Review Programme to hold their own EISCAT time. Another method is to time the rocket campaign with a long-duration (as much as five continuous days) World Day run that has similar scientific aims or a mutually satisfactory radar experiment configuration.
Rocket campaigns can last several weeks as the team waits for the best geomagnetic and meteorological conditions to launch the rocket. This being the case it is likely that the campaign will coincide with other EISCAT experiments, and in the worst case scenario these experiments may be occurring at the same time of day that the rocket is intended to be launched and may be scheduled as a higher priority in a particular slot. The following presents the rules and guidelines for dealing with this possibility.
Prior to scheduling:
When drafting the case for support for an EISCAT experiment in support of a rocket the Rocket-PI* must make it absolutely clear how important EISCAT will be for the launch process. If EISCAT observations are essential for deciding on whether a rocket will launch this must be flagged in the proposal. This will help EISCAT HQ in determining the priority levels when scheduling.
There are key pieces of information in the schedule that must be included. First of all ensure that the contact details for the contact person are accurate and as fully completed as possible. That contact person must be fully informed of the experiment requirements including the constraints on the rocket launch itself. It is helpful if the “Responsible experimenter at EISCAT” has this information as well.
The Notes section should contain the details of the EISCAT experimental setup; e.g. pulse code, pointing direction/scan pattern, etc. This is also a good place to reiterate the level of importance of the EISCAT observations to the launch process.
Key Point: Communication!
If there are time slots where the rocket experiment is lower than 1st priority in the schedule it is important that the Rocket-PI and the other experiment PIs communicate with each other at the earliest possible time. Remember that the schedule is set on the 11th of the month prior to the experiment which should leave plenty of time to discuss the potential clash.
It is perfectly acceptable for PIs to negotiate with each other and although the high priority PI does not have to yield time** it is highly likely (and borne out by EISCAT history) that they will be willing to cede their time if the rocket is likely to launch. When discussing the ‘clash’ of experiments there are some key questions that should be considered.
The Discussion & Agreement
Questions to ask:
- Do the ‘clashing’ experiments share similar goals?
If so why not collaborate?
- Do the ‘clashing’ experiments have similar configurations (pulse schemes, pointing directions, etc)?
If so why not share the data? If the experiments are slightly different could a suitable compromise be reached in the experimental set-up?
If neither of the above are applicable then there is the important question:
- Does the high-priority experiment PI agree to relinquish first priority if a launch looks likely?
If the answer is no then the discussion essentially ends here, though the Rocket-PI might like to attempt appealing to the EISCAT Director if they have a good scientific argument as to why they should be granted first priority over the other experiment.
If the answer is yes then the PIs must discuss the technical aspects for exactly when the rocket experiment can take over first priority.
Things to consider are:
- the changes required in pointing directions and how quick this change can be done (switching the VHF radar from vertical to low elevation would be an extreme case!).
- how quickly the experiments can be swapped
- the flight time of the rocket (for example Black Brandts have a flight time of ~20 minutes) .
- the length of time the rocket experiment remain 1st priority, and what conditions would lead to priority returning to the original experiment – for example the rocket experiment might require some time after the rocket has splashed down to get context for their observations. This time should be negotiated but a reasonable time might be 30 minutes.
- whether there is a need for the rocket experiment to ‘reimburse’ lost time in terms of donating future 1st priority slots.
- What should happen to the data taken if the rocket is not launched after all? It might be reasonable for the rocket PI to share these data with the original high priority PI.
- In a given campaign, how many interruptions is reasonable? This will depend on the balance of 1st priority slots between the experiments. A reasonable number might be two to allow for one aborted launch and to ensure the original first priority PI does not lose too much time.
Some useful information about rockets launches:
For the rocket countdown, T-15 minutes is effectively the lowest a count can go before swapping priority. If the experimenters wait too long after this there is a real danger there will be not enough time to swap the experiment mode and fully capture the data that the rocket experiment needs.
At T-15 minutes there is a very real intent to launch; however EISCAT observations might be needed for a final decision and this should give time for a decision to be made. It is possible that there may be small holds (for example at T-3 minutes); however it would not be reasonable for the rocket experiment to retain first priority indefinitely. That said, the amount of hold time will be limited by the rocket range. If the countdown reaches T-15 a good compromise might be to give the rocket experiment a 30 minute window. If there is no launch within that time-frame the time is relinquished back to the original 1st priority experiment (assuming it is still within their allocated slot).
This all sounds like a lot of work but please consider: the parts about scheduling are best practice for what should be done anyway. The discussion and agreement can be sorted in just a few minutes in most cases as long as the PIs have all the information they need about their respective experiments.
* here Rocket-PI refers to the PI of the EISCAT experiment in support of the rocket, this may be different to the PI of the experiments on board the rocket.
** It has always been EISCAT policy that the PI of the highest priority experiment decides whether they wish to run in a given slot and if not the 2nd priority will run and so on to lower priorities (this also depends on whether any experiments have decided to cancel in those time slots – always keep an eye on the schedule). It is good practice for the high priority PI to inform lower priority PIs whether they are running or not.