Instrument: Ca+ measurements were made using one of the resonance lidars at Arecibo, which is based on a Nd:YAG laser pumping a dye laser at its frequency doubled output at 532 nm [Tepley et al., 2003; Raizada et al., 2011]. To generate the resonance wavelength of Ca+ at 393 nm, we used a DCM dye tuned to 624 nm. This wavelength is then sum-frequency mixed with the residual Nd:YAG fundamental, giving an average power of 0.8 W at 393 nm. A Cassegrain type f/15 telescope with 0.8 m diameter was used as a receiver. Photons at 393 nm are either detected by an EMI photomultiplier tube (PMT) attached at the back of the telescope or are directed to a Hamamatsu PMT using a 1.0 mm core optical fiber. The background is reduced using a narrowband interference filter having a FWHM ~ 1 nm. Finally, the data is recorded using a multi-channel scaler with a range resolution of 37.5m or 75 m depending on the signal strength.
Observations: 30 nights over two years when Ca+ data was obtained using a resonance lidar at Arecibo, 15 each during summer (May to July) and winter times (October to December).
Paper submitted: Raizada, S., C. Tepley, B. Williams, R. Garcia, Summer to Winter Variability in Mesospheric Calcium Ion Distribution and its Dependence on Sporadic E at Arecibo, J. Geophys. Res., submitted, 2011.