CINDI (Coupled lon-Neutral Dynamics Investigation)

What is CINDI?

CINDI is an investigation to study the dynamics of the equatorial ionosphere, which is influenced by the collisions between the charged and neutral gases in the upper atmosphere. The NASA-sponsored investigation carried ion and neutral sensors designed and built at UT Dallas as part of a more extensive payload for the Communications Navigation Outage Forecast System (C/NOFS). The C/NOFS satellite was launched from a Pegasus vehicle in April 2008 and continued to provide data until the satellite re- entered the atmosphere in 2015. The operation of the payload was supported by the US Air Force and provided an unprecedented view of the formation and evolution of ionospheric structures that are detrimental to space-based communication and navigation systems.

Mission Objectives

CINDI/CNOFS combines space-based observations of ionospheric density and motion and ground-based observations of phase and amplitude scintillations on radio signals that pass through the ionosphere. These data sets provide information on the conditions that prevail when ionospheric structures are formed and the relationships between these structures and the degree of interference that they produce of the ground. Observations over a range of longitudes and local times provide us with an understanding of the effects of the magnetic field orientation as well as season and solar activity on the appearance of ionospheric structure.

CINDI Instruments

UTD provided two complementary instruments for the mission science investigation. The lon Velocity Meter (IVM) was based on legacy sensors, including the ROCSAT-1 IPIE, and formed the basis for instruments later provided for the ICON and COSMIC-2 missions. The IVM was composed of two plasma sensors, the lon Drift Meter (IDM) and the Retarding Potential Analyzer (RPA). The Neutral Wind Meter (NWM) consisted of two newly developed neutral gas sensors, the Cross Track Wind Sensor (CTWS) and the Ram Wind Sensor (RWS). Together these instruments measure the motion, temperature, composition, and density of the ionized and neutral gas along the path of the satellite on orbit.

CINDI Activities

CINDI data was the first to describe the size of the ionosphere at times of very low solar activity. During extreme solar minimum the O+/H+ transition height of the ionosphere was found to be significantly smaller than predicted by reference models of the time [Heelis et al., 2009]. CINDI data also detailed the plasma motions that occur during periods of low solar activity, which are very different from those previously seen during moderate and high activity. A large semidiurnal component in the ion drift variation at the equator led to upward ion drifts at midnight, the opposite of the typical behavior with higher solar input [Stoneback et al.].

The CINDI project sponsored a significant education and outreach activity that included teacher workshops, conference presentations, and published three comic books aimed at explaining space science to middle and high school students. Inspired by the name of the mission, the comic books followed the adventures of “Cindi”, an android spacegirl and dog catcher whose robot dogs serve as metaphors for the charged and neutral particles the CINDI instrument studied. The comic books are available on-line in English and Spanish at cindispace.utdallas.edu.

References

Heelis, R. A., W. R. Coley, A. G. Burrell, M. R. Hairston, G. D. Earle, M. D. Perdue, R. A. Power, L. L. Harmon, B. J. Holt, and C. R. Lippincott (2009), Behavior of the O+/H+ transition height during the extreme solar minimum of 2008, Geophys. Res. Lett., 36, LO0C03, doi: 10.1029/2009GL038652.

Stoneback, R. A., R. A. Heelis, A. G. Burrell, W. R. Coley, B. G. Fejer, and E. Pacheco (2011), Observations of quiet time vertical ion drift in the equatorial ionosphere during the solar minimum period of 2009, J. Geophys. Res., 116, A12327, doi:10.1029/2011JA016712