LIP

Point of Contact:

Richard Blakeslee

Global Hydrology and Climate Center

NASA/ Marshall Space Flight Center/ Code: HR20

Huntsville, Alabama  35806

Office Telephone: (256) 922-5962

FAX: (256) 544-1777

E-mail: rich.blakeslee@msfc.nasa.gov

Brief Instrument Description of the
Lightning Instrument Package (LIP)

LIP as it presently exists (unchanged from CAMEX2) is described first. We are also planning to augment the LIP package for the TRMM validation missions now being planned for the spring of 1998 (see Instrument Augmentation below). This augmentation would support the CAMEX3 missions as well.

Instrument Description

The ER-2 LIP consist of two electric field mills, a conductivity probe, and the associated data system. One of the field mills is installed on the upper Q-bay hatch cover and the second one is mounted on the aft section of the Advanced Microwave Precipitation Radiometer (AMPR) faring (or on the lower E-bay hatch cover). The conductivity probe is integrated on the right hand superpod nose cone. The ER-2 LIP data system is mounted in a 19" vertical rack located in the aft section of the ER-2 Q-bay. The ER-2 electric field mills and the conductivity probe are compact sensors, each weighing less than 5 lbs.

The ER-2 electric field mills measure the vertical (E_z) and one horizontal (E_x) components of the electric field over a dynamic range exceeding 3 orders of magnitude (i.e., there are 3 gain channels, x1, x46 and x2116). Hence fair weather electric fields as well as large thunderstorm fields (e.g., 10-20 kV/m) can be measured. The field mills also provide a measurement of the electric charge (Q) on the aircraft. Abrupt electric field changes are used to identify lightning discharges and often cloud-to-ground and intracloud discharges can be distinguished. The conductivity probe provides a measure of the air conductivity at the aircraft altitude. The conductivity probe consist of a pair of Gerdien capacitor type sensors so that contributions due to positive and negative ions are measured simultaneously.

Data products produced by ER-2 LIP system includes

A. Electric field components (E_x and E_z) and aircraft self-charge (Q)
period: continuous record, entire flight
resolution: 10 Hz sampling rate
comments:   Total lightning (cloud-to-ground, intracloud) can be determined from electric field changes  in the data. Data will also provide information on the electrical structure within and around the thunderstorms and hurricanes encountered (often this will be the only means to assess the electrical state of the clouds overflown). The electric currents flowing above storms can be derived using the electric field and air conductivity measurements.

B. Air conductivity
period: continuous record, entire flight
resolution: 10 Hz sampling rate
comments: Simultaneous measurements provided of both polar components of the air conductivity (i.e., contributions from positive and negative ions). Storm electric currents can be derived when used with the electric field data.

Instrument Augmentation

We are planning to augment the LIP package for the TRMM validation missions scheduled to take place during the spring of 1998. This augmentation would provide good additional lightning observations for the CAMEX3 missions. We will install electric field mills on the superpods (3 mills per pod) to measure all components of the electric field (i.e., E_x, E_y, E_z ). The electric field signals will be digitized at each mill and transmitted in an ASCII data stream to a data logger located in each superpod. These sensors and data system are compact and can be installed even in unpressurized locations on the ER-2 (e.g., unused locations on the superpods). In addition, we do not anticipate that any major problems will be encountered integrating these compact electric field mills with other systems that may be flown during CAMEX3 (e.g., MIR, MTS, MAMS). For the TRMM validation missions we also plan to install transient optical pulse sensors and an electric field change sensor developed and flown on the high altitude WB-57 this past summer aircraft during STERAO.