TOPEX Buoy Design Program

Program Synopsis
Design Process Scenario
Project Design Goals
Buoy and Cable Floation System Specifications

Program Synopsis

The University of Texas Center for Space Research (UTCSR) and Texas Space Grant Consortium (TSGC) in conjunction with the Colorado Center for Astrodynamics Research (CCAR) and the Colorado Space Grant Consortium (CSGC) are developing an outreach design program for high school students. The primary objective is for high school students to design and fabricate a prototype shallow water instrumentation platform consisting of a boat and tethered buoy. The buoy will provide a platform for a Global Positioning System (GPS) antenna that will be used to determine the precise horizontal and vertical location of the buoy. The goal of this design program is to calibrate altimeter measurements on Galveston Bay made by an Earth orbiting NASA satellite called TOPEX/Poseidon. TOPEX altimeter calibration requires knowledge of sea height and wave height. The instrumentation to make GPS measurements and the data storage equipment necessary to format and record these measurements are contained in a receiver system which will be provided to the students each time measurements are scheduled. Additional measurement devices will be used to collect observations from either the buoy or the boat in order to better understand the estuarine processes in Galveston Bay. A major goal of the project is for the students to design and build a low cost instrumentation system to collect important scientific measurements.

The following primary and secondary scientific objectives are planned:

1. The primary objective of the program is calibration of measurements from the TOPEX/Poseidon satellite.
2. The secondary objectives include the characterization of bay currents and water properties to better understand the motion and condition of water in the bay. Such measurements will enhance monitoring and prediction of circulation in the bay for understanding the dispersion of pollutants, as well as supporting biological research in the bay.

Design Process Scenario

This scenario is provided for illustrative purposes, and will not be exactly followed by any of the teams participating in the project. The ultimate product will be a student designed and built buoy, tended from a boat. Additional instrumentation can be used to measure air and water properties during the "mission".

In January, teachers who are potential team sponsors in the Galveston Bay and Boulder areas will be identified. Teachers will be chosen to lead and supervise student teams at their schools. The teachers will identify and recruit 4 to 6 students each to participate in the project. In early February, a representative of the local Space Grant Consortium will visit each team to help orient the students to the design process, answer questions, and explain more about the project.

Each student design team will be provided with:

Each student design team will spend approximately one (1) month in developing a workable design on paper for their buoy and cable floatation system, along with a plan for measuring other parameters. This proposal will consist of:

In early March, the design teams will submit their design proposals to a review panel made up of personnel from the sponsoring agencies. The panel will analyze the student designs, provide feedback, and suggest changes and improvements to the designs. The review panel will recommend the allocation of funds to the student teams for the construction of the buoys and cable floatation systems. The funds to construct the buoy and cable floatation system will be provided to the sponsoring teacher.

Between mid-March and mid-April the buoy and cable floatation system will be constructed. During this period, the students will also complete and submit specifications for the additional instrumentation to be carried on the boat. These specifications must include instrument descriptions (these can be obtained from the manufacturers), instrument costs, and vendor identifications. Teams are encouraged to solicit donations of instruments for their systems.

Between mid-April and mid-May the teams are encouraged to test their buoys. When a workable design has been built the teams should contact the project office to arrange for a GPS receiver to be delivered for final testing. This test will depend on GPS availability.

In mid to late May, a "Float-Off" will be scheduled. This will be a one day exercise combined with a picnic. A full set of instrumentation, a boat, GPS receivers, and review personnel will be provided to facilitate the testing. Those invited to participate will include all team members, their sponsoring teachers, personnel from the sponsoring organizations, technical review team members, and selected NASA personnel. This event will provide students an opportunity to test their design by collecting data and comparing their results with the other design teams.

Over the summer and into the fall, students, sponsoring teachers, and project personnel will use the systems to take data on Galveston Bay at ten day intervals. This means that each team will be active about once per month.

Description of Existing Buoys

The following system description is provided to describe what has been done in the past. Student design teams are welcomed to follow the approach described, but are encouraged to explore alternate systems.

Description of a Hypothetical Buoy System

It is envisioned that the buoy will be connected to a boat by a floating cable and the GPS antenna will be mounted on the buoy. The GPS receiver itself would be located in the boat. The student designed buoy might also carry several student selected instruments for measuring the characteristics of Galveston Bay and the water in it. However, it is likely that most student selected auxiliary instrumentation would reside on the boat. Students on the boat would be active in reading these instruments, making measurements, recording data, taking samples, etc., throughout each "buoy mission".

The buoy will be deployed and collect data over a period of several hours at selected locations in Galveston Bay. The buoy will be tended during this time by a drifting boat. The boat crew will be comprised of a few members from the student/faculty/mentor design team. The students will be taking measurements of bay and atmospheric conditions at each of the buoy locations while the GPS is collecting positional data. The sequence of events is seen as (1) move buoy and boat to a data collection site in the bay, (2) Deploy the buoy from the boat and collect data for approximately an hour, (3) move the buoy to another location, (4) collect data, etc. It is anticipated that high school student/faculty/mentor teams will be involved in the entire cycle of design, production, deployment, tracking, recovery, re-deployment.

Project Design Goals:

A. Calibration of the TOPEX/Poseidon altimeter

The TOPEX/Poseidon altimeter provides measurements of the mean sea level, sea state, and wind speed. The primary goal of this design project is to provide a means of calibrating altimeter measurements from the TOPEX/Poseidon satellite. This calibration is done by determining the mean sea level above a reference position. By mounting a GPS receiver to a moveable platform, the height of the platform can be determined to within 1 cm. The buoys will be positioned near the satellite ground track (the satellite crosses directly over Galveston Bay at ten day intervals) and will collect data as the satellite is passing overhead. The buoy and auxiliary instrumentation should be able to provide the following to support the altimeter calibration:

1. Mean sea level above a reference ellipsoid with wind waves removed to at least 1 cm rms over each fifteen-minute interval measured. The GPS receiver will provide this measurement as long as the buoy provides a verifiable antenna to water level distance.

2. Sea state every five minutes with an accuracy of 0.5 meters of 10% -- whichever is greater. For a floating platform, the GPS data will provide this information.

3. Wind speed with an accuracy of two meters per second. Wind speed measurements can be taken from the boat, making sure that the boat is not interfering with the measurement.

B. Monitoring environmental conditions in Galveston Bay

A secondary goal of this project is to collect environmental data from Galveston Bay. This type of data is necessary for understanding oceanic and atmospheric dynamics and provides an excellent learning experience for students. It is important for the co-existence of industry and the environment to be able to minimize the impact of pollution on marine life. To do this, it is important to understand the nature of currents and mixing processes in the bay. Additional measurements could include:

1. Atmospheric conditions including temperature, wind speeds, barometric pressure, and relative humidity.

2. Water conditions including temperature, salinity, turbidity, and nutrient concentrations. Several of these measurements might be carried out by collecting water samples for analysis later. If these types of measurements are chosen by the student teams, procedures for water analysis or sources for outside analyses of samples must be considered.

Buoy and Cable Flotation System Specifications

Physical Requirements:

Additional Measurements


Last Modified: Fri, Aug 20, 1998