PUNCH News

Downlinking data from space costs money. PUNCH generates a lot of data, which drives the cost of operations – so we do everything we can to reduce the size of each image. We can’t use “lossy” compression algorithms, since a lot of the PUNCH science lives in very faint fluctuations that would be discarded in compression. Coming out of the camera, each WFI image is 8 Megabytes (MB) of 16-bit values. Using JPEG-LS (a lossless algorithm) on the raw images would reduce them to about 3 MB each. But we can (and do) squeeze them further.

PUNCH images of space are now available for download from NASA’s Solar Data Analysis Center (SDAC), in scientific-grade FITS format with relevant pointing and spacecraft-status metadata included. The data are updated twice daily by SDAC from the Science Operation Center (SOC) servers at Southwest Research Institute (SwRI) in Boulder, Colorado – and will continue to update as data arrive from space and are processed by the SOC. The data are also being indexed by the Virtual Solar Observatory. The PUNCH website includes links to documentation for the data and for the mission. Many thanks to Marcus Hughes (PUNCH SOC Lead), Jack Ireland (SDAC Lead), and their teams for opening the taps.

Commissioning of the PUNCH instruments is ongoing. As part of that activity, we ran the first full-orbit NFI (Narrow Field Imager) science sequence on Sunday, April 27. NFI captured several images of the Moon passing by the Sun in the sky, as seen in this unfiltered “Level 0” image in the standard PUNCH pseudocolor palette. The new Moon appears full, because it is illuminated by Earthshine from the full Earth (as seen from the lunar surface). This image is useful to demonstrate that the Moon does not directly interfere with NFI’s primary science, as it is not bright enough to impact the existing pattern of glinting stray light.

There've been lots of stories about this week’s triple-conjunction smiley moon in the media. We happened to catch the conjunction during PUNCH commissioning, along with two other planets besides!

This beautiful, ghostly polarimetric rainbow reveals the direction and degree of polarization of the ghostly zodiacal light, in a preliminary data product from the WFI-2 spacecraft. On 18-April, WFI-2 executed its first polarimetric triplet imaging, collecting images through all three of its polarizers in succession. The polarimetric triplet image, expressed as RGB color channels, reveals the direction (via hue) and degree (via saturation) of polarization everywhere in the field of view all at once. WFI looks to one side of the Sun (marked with a star glyph). This image, made with Level 0 (uncalibrated) data direct from the WFI-2 camera, is consistent with existing results (Leinert et al. 1998) on the direction and degree of polarization of the zodiacal light. Stars appear white because they are mostly unpolarized compared to the 7% polarization of the zodiacal light. PUNCH uses a novel mathematical formalism (“MZP”, DeForest et al. 2022) to manipulate and background-subtract the polarimetric values from each of its four cameras. Chromatic treatment of coronal polarization was demonstrated at the 2023 total solar eclipse (Patel et al. 2023), highlighting the long-term synergy between ground- and space-based observations of the corona.

PUNCH opened the protective doors of its first two instruments, the Narrow Field Imager (NFI) and one of its three Wide Field Imagers (WFI-2) on 14-April. First-light images from WFI and NFI reveal that they are in focus, functioning nominally, and able to collect the deep field images needed for PUNCH science. The first image from WFI-2 is a spectacular view of approximately 40° of sky, including zodiacal light, several constellations, and various other astronomical objects. The first image from NFI reveals in-focus performance and resolution of the faint starfield close to the Sun. These two images are composited here to show how the instruments’ data will fit together once commissioning is finished.

During the week of 2025 April 7, PUNCH collected calibration data from the instruments – our last chance to take advantage of closed doors, before they open. Even these “dark frames”, taken with the doors closed, are interesting to look at. These images are “Level 0” (unprocessed) data products generated by the Science Operations Center (SOC), with full flight metadata attached. The cameras are working properly, with low noise levels. The images are brighter on the right because PUNCH uses dual readout detectors, with separate digitizers for the two halves of the images; they have slightly different zero points, an effect we remove at “Level 1” and higher. There is a very small amount of light visible in the upper left, which we believe is stray light scattered by the closed instrument door itself. Over the South Atlantic Anomaly in Earth’s magnetic field, an area of enhanced cosmic ray flux, we see significant particle impacts on the detector. The rate of impacts agrees with calculations performed over six years ago, during the mission’s Phase A concept study.