<div align="left">Space Instrumentation Lab</div>

Sudden Atom Layer (SAL)

The NASA Sudden Atom Layer sounding rocket was launched as a part of the COQUI II campaign from Puerto Rico on 19 Feb 1998.  The rocket’s main scientific purpose was the probing of sporadic sodium layers (Nas).  These are thin (1 km) layers of neutral atomic metal that form in the mesosphere (as observed by lidar), roughly within an altitude range of 90-100 km. 

Three of the onboard instruments that USU/SDL contributed were:

  1. a radio frequency Swept Impedance Probe (SIP) for electron density measurements and
  2. a fixed bias (DC) Langmuir Probe (DCP) for relative electron density measurements.

The payload included a charged dust detector, a Langmuir probe that operated as a Fast Temperature Probe to measure electron temperature, telescopes to measure sodium airglow, and photometers and lamps to measure neutral sodium density.  The figure below depicts the payload instrument configuration.

The SIP successfully measured electron density and along with DCP provided valuable insight into the electron density structures associated with sudden sodium layers in a collisional plasma.
The data is shown below.

The payload reached a maximum altitude of 115.5 km and flew through two thin sporadic sodium layers at 94 km and 97 km, with peak densities of 6000 cm-3 and 4000 cm-3, as determined by the ground based sodium lidar.  Also detected was a sporadic-E (Es) layer at 92.5 km by the Arecibo radar.  The charged dust detector was mounted on the nose of the payload and an attitude control system was used to point the nose in the ram direction for the upleg as well as the downleg portion of the flight.  It observed a 5 km thick positively charged dust layer accompanying the lower Nas layer [1].

 

[1] Gelinas, L., K. Lynch, M. Kelley, S. Collins, S. Baker, Q. Zhou, and J.S.Friedman (1998), First observation of meteoric charged dust in the tropical mesosphere, Geophys. Res. Lett., 25 (21), 4047{4050.

Barjatya, Aroh.