Abstract: Circadian disruption in shift-work is common and has deleterious effects on health and performance. Current efforts to mitigate these harms reasonably focus on the phase of the circadian pacemaker, which unfortunately in humans, shifts slowly and often incompletely. Temporal reorganization of rhythmic waveform (i.e., the shape of its 24 h oscillation), rather than phase, however, may better match performance demands of shift-workers and can be quickly and feasibly implemented in animals. In fact, a bifurcated pacemaker waveform may permit stable entrainment of a bimodal sleep/wake rhythm promoting alertness in both night and daylight hours. Although bifurcation has yet to be formally assessed in humans, evidence of conserved properties of circadian organization and plasticity predict its occurrence: humans respond to conventional manipulations of waveform (e.g., photoperiodism); behaviorally, the sleep/wake rhythm is adaptable; and finally, the human circadian system likely derives from the same multiple cellular oscillators that permit waveform flexibility in the rodent pacemaker. In short, investigation into untried manipulations of waveform in humans to facilitate adjustment to challenging schedules is justified.

Abstract: Artificial night lighting is a unique sign of human activity. Pictures from space show us
beautifully and strikingly how we illuminate our planet. Light emission (and low-light
reflection) data can aid research in numerous fields, from socio-economic studies, via light
pollution, to emergency response. The only instrument currently capable of measuring
nighttime lights from space is the Defense Meteorological Satellite Program – Operational
Linescan System (DMSP-OLS). Although this unique dataset was the first to allow analysis
of our nighttime activities, it has many shortcomings, such as rather coarse spatial resolution
(2.5 km ground sampling distance), only panchromatic visible spectral information and no
visible band calibration, 6-bit quantification, saturation and overglow. By the end of 2011, a
new instrument will be launched, the Visible-Infrared Imager-Radiometer Suite (VIIRS)
onboard the NPOESS1
Preparatory Project (NPP) satellite. This instrument remedies some of
the shortcomings of the DMSP-OLS instrument, but it still is not designed for earth
observation of nighttime lighting and lacks many specifications we advocate here. On June
10th 2011, the High Sensitivity Camera (HSC) onboard the Aquarius/SAC-D satellite was
launched successfully. This instrument has a panchromatic band (450 – 610 nm) and a
resolution of 200-300 meters. The foreseen products and other characteristics are yet
unknown to the authors.