19-00989_-_NRMAG000-19-00989_STATEMENT_OF_NEED_EFM_-_CS_FBO.pdf

STATEMENT OF Work Requiring Office Name: National Severe Storms Laboratory

NRMAG000-19-00989

1. Background and Purpose

One of the grand scientific challenges of NSSL is to predict lightning. In order to achieve this challenge we must improve understanding of thunderstorm electrification and electrical breakdown processes which contribute to lightning production. NSSL has been a world leader of in-storm measurements including instruments such as our balloon-borne electric field meter (EFM). Such in situ measurements are critical to evaluate electrification hypotheses and to provide valuable background information for simulating storms and for interpreting some radar observations related to lightning initiation. The NSSL EFM is regarded as the standard within the field against which other EFMs are evaluated. Unfortunately, with advancing technology some of the internal electronics have become obsolete and can no longer be repaired. In order to sample the in-storm electric fields and to continue providing the standard against which any future technologies for electric field measurements can be evaluated, we must rebuild the internal electronics in the existing EFM sensor.

2. Scope and Objectives

This acquisition is for the necessary redesign of the internal electronics of the balloon-borne EFM and for the addition of new capabilities to make operation and data analysis easier, to address the scientific problem outlined in Section 1. The following figure shows the external structure of the EFM, with components labeled for use in the rest of this Statement of Work. The redesign will be housed within this basic external structure, which NSSL will provide, and should not cause the EFM to violate FAA regulations for free-flying balloons outside of protected air space.

The present electronics package includes an analog circuit inside one of the two aluminum spheres, with the other sphere providing circuit ground. The analog circuit contains a charge amplifier and produces a signal proportional to the charge flowing between the two spheres. This signal is fed through a 12-bit analog-to-digital converter which produces output that is recorded on an SD card within the EFM, and decimated values are transmitted through an antenna in one of the vanes to a radio receiver in NSSL’s mobile laboratory on the ground. The dynamic range of the electric field measured by the present instrument is approximately from -200 kV/m to +200 kV/M. The present electronics package also includes a three-axis accelerometer and a three-axis magnetometer which together provide measurements of the three-dimensional orientation of the axis through the centers of the two spheres, so that we can determine the direction it is pointing when the spheres are aligned with the electric field vector.

The redesigned electronics shall provide essentially the same or better measurements of the electric field vector, shall record data internally on an SD/micro-SD card, and shall transmit decimated data at selectable frequencies in the 400 MHz band used by NSSL receivers.

Figure caption: External structure of the electric field meter (EFM). The component of a storm’s electric field along the axis between the two spheres induces charge on each of the spheres, which are insulated from each other. The vane motor spins the spheres perpendicular to the fiberglass tube at approximately 2 Hz, and the wind vanes cause the tube to rotate around the roughly vertical balloon train approximately 3 times per minute (0.05 Hz). The combination of the spin and rotation causes charge to flow through an electric circuit between the two spheres as the axis between the two spheres sweeps through essentially all possible directions. The magnitude of the induced charge is largest when the two spheres are aligned with or opposite to the electric field vector.

Besides redesigning the present electronics, new capabilities shall be added to facilitate instrument flight operations and data analysis. These shall include the following, which are described more fully in Section 3: (1) New spin motor and controller to maintain a constant spin rate of approximately 2 Hz for the two-sphere assembly throughout a balloon flight, (2) GPS time and location, and (3) An external device to be placed in the balloon train to detach the instrument from the balloon at a specified altitude or pressure or received radio signal and at a fail-safe elapsed time. If a circuit component on any of the internal circuits provides an onboard measurement of temperature or pressure, these measurements shall also be recorded on the SD/micro-SD card, along with the other data that shall be provided by the redesigned electronics as described in Section 3.

Three copies of a complete prototype of the new design shall be delivered to NSSL for testing by 120 days after contract award, preferably by September 23, along with complete operating instructions and all documentation needed to receive and analyze the transmitted and on-board recording of the data. Three copies are needed to ensure one successful flight in the hazardous environment of storms. When suitable weather and adequate NSSL personnel are available, NSSL will fly the prototype in conjunction with an existing EFM to evaluate proper performance of the redesign and of the new capabilities. Issues identified by NSSL as a result of the test flight will be corrected by the vendor to produce a final product, which shall be delivered to NSSL along with complete documentation within 60 days of receiving NSSL’s evaluation, after which NSSL can begin modernizing the existing EFM inventory for future field use by summer 2020.

Given the harsh conditions and ground impacts experienced by balloon-borne instruments within thunderstorms, this design requires full documentation for future repairs of individual modules by NSSL technicians.

The EFM with modernized electronics will be evaluated against a complete, existing unit in fall/winter 2019, subject to weather conditions and availability of NSSL personnel, after which we hope to begin modernizing the existing EFM inventory for future field use by summer 2020.

Additional selection criteria: At least five years experience with meteorological or electric field instrument design. Experience with balloon-borne instruments, knowledge and understanding of the current EFM design is also required.

3. Product Specifications

Line Item #1. Electronics and Firmware Design Update/Labor Quantity 1

For the existing EFM sensor with equal or better performance than currently with modern components

General design specifications:

• Provide guaranteed operation for at least 100 minutes at -20 °C and for at least 30 minutes at -40 °C.

• Reasonably resist moisture intrusion from the in-storm environment.

• Be calibrated inclusive of thermal response from -40 to 40 °C.

• Match the gain and response function of the current analogue design with the same or greater dynamic range.

• Maintain the same binary format of the decimated data transmitted at standard frequencies in the 400 MHz band allocated to ballooning for weather operations and research

• GPS time and location shall be interleaved in the full EFM data stream recorded onboard in a SD/micro-SD card

• All electronics must be easily activated at launch.

• Electronics and hardware shall be resistant to landing shock when instrument lands with a parachute after separating from balloon

• Design shall consider the ease of future repairs following damaging instances.

• Finished unit shall meet FAA regulations, as is done by the current design.

• Full design documentation inclusive of hardware design and any software or firmware installed onboard shall be provided by the end of the contract. Full documentation of the modernized components shall include directions for installing and repairing the electronics, instructions for operating the electronics and for accessing both the transmitted data and onboard recording of the data output by the electronics, source code for any firmware used by the electronics, and the schematics and PCB layout for the electronics in a standard format. Given the harsh conditions and ground impacts experienced by balloon-borne instruments within thunderstorms, this design requires full documentation for future repairs of individual components by NSSL technicians.

Individual components to be modernized shall include:

• Electronics Within the Spinning Spheres – the analog charge-amplifier circuit and the analog-to-digital converter for digitizing the analog output shall be installed within a single sphere and shall use the opposing sphere as circuit ground. The charge-amplifier circuit shall match the gain and response of the present unit, and its dynamic range shall meet or exceed that of the present unit. The analog-to-digital converter shall sample and convert the analog output at least 25 times per second (a 25 Hz rate) with at least 12 bits of resolution. The digital electronics in this sphere shall contain an inertial measurement unit consisting of a gyroscope, a three-axis accelerometer, and a three-axis magnetometer and shall be installed in such a way that the three-dimensional orientation of the line passing through the center of both spheres can be determined.

The inertial measurements shall be sampled and added to the digital data stream at the same time as the analog charge-amplifier output is sampled, although the inertial output may be interpolated if necessary to determine its value at the time of the charge amplifier sample. If the electronics within the sphere provide temperature and pressure measurements of the environment inside the sphere, these measurements will be incorporated at regular intervals in the data stream recorded on the SD/micro-SD card which is in a wind vane. Alternatively, if digital temperature and pressure measurements are provided by the electronics unit in the wind vane described below, those data may be incorporated instead. Digital data from the spinning spheres shall be provided to the electronics in the wind vane by a fiber optic cable passing through an existing non-spinning hole in the fiberglass tube.

• Spin Control Unit – a small motor shall be installed within one of the wind vanes and shall spin the two- sphere assembly about the fiberglass rod at a rate of approximately 2 Hz. The control unit shall monitor the rotation rate and maintain a constant rate throughout the duration of the flight. When rotation is stopped after launch either by ground impact or by another impediment such as excessive icing in the storm, the spin motor shall be disconnected from electric power.

• Recording, Transmission, and GPS Electronics – a low-profile GPS antenna shall be mounted on top of one of the wind vanes. Electronics within that wind vane shall provide GPS time and location, shall receive data through the fiber optic cable from the electronics in the spinning sphere, and shall record the GPS time and location merged with the full digital data stream from the spinning spheres on a local SD/micro-SD card.

During each flight, the electronics shall also transmit decimated data from the spinning sphere, preferably with periodic GPS location data, by 400 MHz radio using standard user-selected frequencies to a receiver provided by NSSL in its mobile laboratory.

• Cutdown Module – a separate unit shall be provided for installation in the balloon train above the parachute to terminate the connection with the balloon (1) at a selectable elapsed time period ranging from 30 to 120 min to provide fail-safe detachment in case the alternative means for detachment fails and (2) at one or more of the following: a selectable pressure, selectable altitude, or operator signal (via satellite phone or 900 MHz radio). Detachment shall not use a squib or other explosive, but shall be by cutting or melting one point in the balloon-train line above NSSL’s parachute, preferably in such a way that any electronics in the cutdown module return with the EFM.

Line Item #2. Prototype Quantity 3

Each prototype shall include all components within Line Item 1. Prototypes shall be ready for test flight alongside an existing EFM unit by 100 days after contract award, preferably by September 23, 2019, and shall include manual-style documentation containing instructions for installing the prototype electronics within the existing EFM structure, for activating the prototype shortly before launch, and for reading and decoding both the transmitted data and the data recorded on the SD/micro-SD card. Three prototype sets are required to ensure a test in spite of the unavoidable uncertainties of testing in storms, which contain hazards to the EFM.

Line Item #3. Calibration/Testing/Revisions

As needed to meet all requirements within Line Item 1 for future production units for modernized EFM instruments.

Line Item #4. Delivery

4. Price Consideration: Price by line item

5. Requested Delivery/Period of Performance: One year from date of award.

6. 12 month Option Period(s) Added: N/A

7. Point of Contact for this Action:

Administrative

TO BE PROVIDED AT TIME OF AWARD.

Technical

TO BE PROVIDED AT TIME OF AWARD.

All at:

NOAA/OAR/NSSL

120 David L. Boren Blvd., Norman, OK 73072

8. Ship to Address

Shipping: Send invoice to:

NOAA/OAR/National Severe Storms Lab nssl.invoice@noaa.gov Attn: TO BE PROVIDED AT TIME OF AWARD 120 David L Boren Blvd Invoice Contact:

Norman, OK 73072 TO BE PROVIDED AT TIME OF AWARD