The AIM spacecraft continues to perform well.
Prior to temporarily powering down on 11 August, CIPS had successfully monitored PMCs throughout the NH 2016 season. A new retrieval algorithm, version 5, was implemented to handle the new "constant imaging" viewing mode, in which CIPS images are acquired every 3 minutes throughout the orbit, rather than every 43 seconds over the summer polar region. This retrieval algorithm is also being adapted to retrieve gravity wave signatures near an altitude of 50 km. After a relatively slow start, the NH PMC season was fairly average until late July, at which time there was a steep decline in PMC frequencies that lasted about a week before recovering to normal levels. The cause of this decline is being investigated.
The plot here shows the ascending node PMC frequencies at a latitude of 80°N for all seasons observed by CIPS; the latest date in 2016 is 5 August. Seasons prior to NH16 use the version 4.20 algorithm, whereas NH16 uses the version 5 algorithm. The very high values in 2015 and at the end of the NH14 season are artifacts caused by false detections when viewing at very high beta angles. The version 5 algorithm fixes this error, and is being applied to data from all seasons for robust inter-seasonal comparisons. The CIPS instrument is expected to be turned back on in early September.
Figure caption. AIM/CIPS daily PMC frequencies at 80°N latitude for all NH seasons observed by AIM.