Jovian Impacts Detection Software

Software algorithms

JID & DTC

In both cases the software performs differential photometry of the area covered by the planet. The idea of differential photometry was proposed by Emil Kraaikamp in a personal communication.

Basically a reference frame is taken at the beginning of the video sequence and later frames are compared with it so that differential photometry of the whole planet is computed. This is demonstraded in the image shown on the right where the spot covered by the impact flash departs clearly from the rest of the planet. To achieve this goal, all the frames in the sequence must have the planet centered (registered). A simple algorithm based on finding the Center of Brightness (CB) position is implemented together with an estimation of the planet size in the video from horizontal and vertical scan centered on the CB pixel.

Then the software computes the total signal of the differential photometry for all frames. Due to the seeing effects the planet limb contributes strongly to the photometric signal. The software assumes an impact departs strongly from the rest of the planet and looks for the frames with the pixels with the uppermost differential photometric value. The software orders the frames in terms of the strength of the most intense pixel and compares them sequentially identifying those consecutive frames where pixels with the strongest signal are found. It correctly identifies impacts in video observations of the June 2010 impact in Jupiter.

For JID software further details are provided in this link (in Spanish) and in the software manual.

Modifications to the main algorithm

JID
• False positive filter (Version 1.2.0 and later, created 10/10/2012)
The search algorithm verifies that the brightest pixel in the image representing an impact is not an isolated event. The search algorithm performs its search in a small box area of 3x3 pixels asking that the brightness in all that region is above the brightness threshold with respect to the average frame.

DTC
• Image summary (only available in DTC software version 0.7.0 and later)
Marc Delcroix suggested an improvement of this idea which can also detect the fainter photometric signal of less intense bolides or bolides observed with moderate equipment. The algorithm consists on the following steps:


- Alignment of all frames.
- Calculate of an average image.
- Build a "maximum brightness image" made considering the maximum value in each pixel.
- Computation of a final "detection image" obtained as the substraction of the average and the maximum brightness image.

Examples of these images are provided on the lower row.