GONG operates as a ground-based network of six observing stations distributed around the globe. Although the network routinely provides high-cadence observations with an exceptionally high duty cycle, periods of reduced coverage occasionally occur. The duty cycle can be adversely affected by several factors, including instrument malfunctions at one or more sites, scheduled maintenance activities, and unfavorable weather conditions.
For more
than two weeks, GONG has been experiencing persistently low duty cycles, as
illustrated in the attached figure. Large gaps in daily coverage are readily
apparent. It appears that the ongoing strong El Niño conditions have been
contributing to severe weather at two of the network's sites, Big Bear (USA)
and Cerro Tololo (Chile), resulting in significant impacts on GONG
observations.
The Mauna
Loa (Hawaii) site remains offline following the volcanic eruption of late
November 2022 and has not yet returned to operational status. In addition, the Learmonth
(Australia) site is currently non-operational due to a technical issue.
Consequently, the Udaipur (India) and El Teide (Spain) stations
have been providing the majority of the network's observations during this
period.
The reduced
duty cycle has a direct impact on the quality and availability of GONG data
products. In particular, when the duty cycle falls below approximately 80%, the
far-side helioseismic maps become increasingly noisy and unreliable.
Consequently, these maps may not be generated during periods of insufficient
data coverage.
NISP
produces far-side maps twice each day using GONG Doppler observations to
identify active regions and emerging magnetic activity on the far side of the
Sun. As a key space weather data product, these maps provide advance warning of
potentially active regions before they rotate into Earth view, thereby
supporting operational forecasting and mitigating space weather risks.
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