Long-Term Data Acquisition, Command, and Control of Spaceflight-Quality Laser Systems
- Sunday, 01 January 2012
NASA Goddard Space Flight Center is a leader in developing satellite-based laser technology for remote sensing measurements of the Earth and other planetary bodies. Laser performance for such missions must be highly efficient and stable over long periods of time in order to successfully accomplish the desired science goals of these missions. It is therefore critical to be able to measure and control multiple laser input and output parameters simultaneously and accurately over a period of time that significantly reduces risk.Currently, for the lifetime testing of the High Output Maximum Efficiency Resonator (HOMER), we use a LabVIEWbased data system on an Apple Macintosh to acquire and analyze images of the laser beam as it exits the laser cavity, evaluate the laser’s performance over time, and monitor and control the environmental conditions under which the laser is tested. One computer attached to multiple cameras and instruments running stable LabVIEW-based software replaces a conglomeration of computers and software packages, saving hours in maintenance and data analysis, and making very long-term tests possible.
When characterizing breadboard laser systems destined for spaceflight missions, NASA scientists are often forced to use several PCs running multiple applications. These measurements can include, but are not limited to, laser beam quality, power, and temperature. Frequent crashes and updates along with inherent incompatiblities with different software and hardware made long-term tests difficult. After completing the tests because data had to be compiled from several different sources, the task of processing the relevant data from each of the applications took several tedious hours. Also, during these tests, it is often necessary to control the input parameters such as diode current, chiller temperature, qswitch voltage, etc. in order to properly characterize the laser. This would also require either a lab tech physically changing the settings on the equipment or yet another PC.
Especially for laser systems that are at TRL-5 and below and do not have the resources of a spaceflight program at hand, there is a clear demand for a data system that could combine all of these and other features in one application in an affordable and upgradable package. At the most basic level, it would be ideal to have a laser data system that could characterize multiple beams while also tracking the laser output power and control the input current going to the laser system in a breadboard format. A more complex system would allow for tracking or controling more paramaters such as temperature, q-switch voltage, laser timing, and others.
The primary challenge lies in the compatibility concerns of tracking laser data from multiple sources, as well as controlling hardware from several different vendors. This was the initial spirit of using LabVIEW in designing our own in-house system since it has the capability to accomplish that task. The problem with this solution is that the allin- one solution is not a commercially upgradable product that actively keeps up with advances in technology. Any upgrade to the current system requires design time and contracts to support that effort, which has inherent inefficiencies. Challenges will also occur because it will be difficult to make a product that can work well across a wide range of laser design applications. Another challenge will lie in accurately and consistently measuring multiple beams. Where there are several techniques for making beam measurements that have successfully been implemented by private industry, there is an issue with doing this and capturing the data to NIST standards over a several-month period of time.