José Martínez Heras, Alessandro Donati
The most widely extended approach for automatically detecting anomalous behavior in space operations is the use of out-of-limits (OOL) alarms. The OOL
approach consists of defining an upper and lower threshold
so that when a measurement goes above the upper limit or
below the lower one, an alarm is triggered. Then engineers
will inspect the parameter that is out of limits and determine
whether it is an anomaly or not and decide which action to
take (for example, run a procedure). This is the original out-of-limits concept.
The current OOL concept has evolved to cope with more
situations such as distinguishing between soft and hard limits; for example, a soft OOL triggers a warning to pay attention, a hard OOL triggers an error that demands attention.
Soft limits are contained within hard limits. In addition OOL
thresholds (soft and hard) can be configured so that different thresholds are applicable in different situations (for
example, depending on the working mode of a given instrument).
n Typically, automatic telemetry monitoring
in space operations is performed by out-of-limits (OOL) alarms. This approach consists
of defining an upper and lower threshold so
that when a measurement goes above the
upper limit or below the lower one, an alarm
is triggered. We discuss the limitations of the
out-of-limits approach and propose a new
monitoring paradigm based on novelty detection. The proposed monitoring approach can
detect novel behaviors, which are often signatures of anomalies, very early — allowing
engineers in some cases to react before the
anomaly develops. A prototype implementing
this monitoring approach has been implemented and applied to several ESA missions.
The operational assessment from the XMM-Newton operations team is presented.