Yesterday, I received an overview of my first GBM (GLAST Burst Monitor) assignment. Although the satellite hasn't been launched yet, ground tests have been taking place for quite some time. NSSTC is home to the GBM team in the U.S.; a large number of the high-energy astrophysicists (and other scientists and engineers) here are working on GBM. Since Sandy left, I'm actually the resident expert on Swift (which is weird for me to say) and the only one who really utilizes Swift data, so it's only natural that I start applying my knowledge gained from Swift to assist the GBM team here.

Something I've gotten particularly good at is searching for pulsations using FFTs. When I met with my advisers Chryssa and Bill last week, they recommended I take a look at the noisy data from a low-threshold test conducted recently to find any pulsations in the higher-energy ranges due to the instrument.

I will specifically be looking at the Continuous Time (ctime) data, which has 8 energy channels and a time resolution of between 64 milliseconds to 1024 milliseconds. From what I understand, the lowest energy channel, channel 0 (in the X-ray or low gamma-ray range, I think), is too noisy to be of much use during normal operations.

Data collecting instruments usually have adjustable thresholds which filter out noise. The GBM team conducted a test in which they set the threshold very low, much lower than the threshold would ever be set to while the instrument is in space, so that much of the instrumental and environmental noise was detected. They saw pulsations in the noise in channel 0.

My job is to search the higher channel data taken during that test to determine if the same pulsation is present in any other channels. If it's present during the low-threshold test, there's a chance that it's also present when the threshold is set higher, but may be more difficult to see. When the satellite is launched and the instrument is in normal operational mode, if a scientist detects a pulsation in the data, he/she will want to know if its an instrumental effect.

I've been given the latest GBM science guide, which is only a very short document written in 2004. I've also been given the raw data from the instrument in a binary file which is from a medium-threshold test. The idea is for me to get used to working with this smaller file before they bring me the low-threshold files, which are several gigabytes each, from Phoenix, Arizona.

This is challenging to for two reasons: 1) I've never worked with GBM data before. 2) I've never worked with raw data before, only level 1 data and higher from science center archives. There are several people here who are experts on both, but every single one of them is in the “I'm too busy to breath” mode. I just got the data file this afternoon. After I mess around with it for a while, I'll ask for help if I need it.

Another project that I may become involved in is scanning the old test data for anomalies, but that's in the future, if ever.