If the phenomenon you want to observe is changing on the time scale of hours or longer, you will want to use the "Cadence" option in the Observing Portal.
What is a Cadence?
- A cadence is a sequence of individual requests, evenly spaced in time
- All of the requests share the same target, filter configuration and exposure times
- These requests may be executed on the same telescope, or different telescopes at different sites, in a manner decided on by Serol (the LCO autonomous scheduler)
- Each of the requests is independent of each other; if 1 request succeeds it has no impact on whether the rest will also succeed
How does it work?
The Cadence option is a helper function of the Observing Portal. It allows you to make multiple observations requests, evenly spaced in time.
Period:
The time gap between the individual requests created by your cadence request. For example, if your observing window (set by your start and end time) is 24 hours, and you choose a period of 6 hours, then a single cadence request should create 4 individual requests.
Jitter:
The time flexibility of your individual request windows. For example, let’s say you submit a cadence request with a period of 6 hours, and a jitter of 2 hours. This will create individual requests centred at every 6 hours, with their start and end times +/-1 hour from those centers.
Window start
This changes its normal meaning in the context of a cadence. The window provides the time range where the individual requests will be created. This defines the start of this time range.
Window end
This defines the end of the time range where individual observations will be created.
To create a cadence, go to the Submit Request page on the LCO Observing Portal. In the Window section, change Cadence to Simple Period.
The observing portal will show you all the requests (with individual start and end times) it will create based on your target and time range.
If this matches your intentions, click Apply. These individual requests will be generated when you submit your request.
Are there limitations?
- You cannot split a cadence across an observatory semester boundary (1 February and 1 August, annually). You will need to create a new cadence request for each semester. Copying a request from a previous semester will not produce the correct individual requests, because the Observing Portal will copy the individual requests and not the cadence configuration.
- Large time ranges appear to break in the observing portal. To create the individual requests, the Observing Portal has to calculate the rise/set times for your object at each of our network sites. This calculation can take take a long time.
- Cadence observations of moving objects appear to break in the observing portal. This is again because of performing rise/set calculations to make sure there is a site available to make every request. This moving targets, this calculation can take significant computation resources.