Archive for category JP2Gen
Some of you may have noticed that helioviewer.org was not displaying recent AIA or HMI images in the last 24 hours. This was due to a glitch in the processing pipeline, and we apologize for this. The issue has been resolved and newer images are now coming online. We expect to be caught up within the next few hours. If you spot any problems, please let us know.
We are pleased to announce that the most recent, high quality STEREO images are now available on helioviewer.org.
First off, there are two spacecraft, called STEREO-A and STEREO-B. Both spacecraft orbit the Sun at roughly 1 AU (astronomical unit), or about as far away from Sun as the Earth is. However, STEREO-A is moving ahead of the Earth in its orbit, and STEREO-B is drifting behind the Earth in its orbit. This means that each STEREO spacecraft sees different parts of the Sun, parts that we can’t see from Earth. STEREO-B sees features on the Sun that we eventually see in SDO and SOHO, and STEREO-A allows us to see the continuing evolution of features that we did see in SDO and SOHO.
This plot shows where each spacecraft is now:
As you can see, they are quite far away from the Earth. This puts some operational constraints on each spacecraft that means we get high-quality images two days after they were taken. These are the data we are making available today; images from June 1st 2011, up to the most recently available data will be available initially. We ask for your patience, as we are uploading these images right now. Over the course of the next few weeks we will be making images from earlier in the mission available so that you can explore the Sun from many different angles over the past 4 1/2 years.
The benefit of seeing the Sun from many different angles is apparent when you look at the following three videos of the prominence eruption of June 7, 2011. The first one consists of images from SDO-AIA and SOHO-LASCO
We hope you enjoy these new images! As ever, please let us know if you spot any problems.
We’re working on including data from NASA’s STEREO (Solar TErrestrial RElations Observatory, stereo.gsfc.nasa.gov) mission. It’s a mission consisting of two spacecraft, one drifting ahead of the Earth, and drifting behind, taking images of the Sun and the inner heliosphere. The concept behind the mission is to view the Sun as a three-dimensional object, from which we can better understand its surface structures and how it influences the inner heliosphere. This is the view from STEREO-A, and this is the view of the same event from STEREO-B. Both movies are of coronagraph data taken with the COR2 instrument; both STEREO spacecraft have the same instrument suites onboard.
We hope to have a stream of the very latest STEREO images very soon. Watch this space!
Some of you may have noticed that recent LASCO C2 images are upside down. You can notice this quite easily, as the streamer belts in LASCO C2 do not line up with the streamer belts in LASCO C3. This is due to an error in the way we write out LASCO C2 images. We are diagnosing the problem and will rewrite the affected images shortly. This in itself will be delayed due to the fact that the machine which writes out new LASCO C2 and C3 images will be offline for a couple of days. We apologize for the interruption to our service in the delivery of good quality new and recent LASCO images. Older LASCO images are unaffected, as are HMI and AIA images.
Today we are making available images from the Helioseismic Magnetic Imager (HMI), an instrument on board the Solar Dynamics Observatory. HMI is designed to study oscillations and the magnetic field at the solar surface, or photosphere. We are providing line-of-sight magnetograms and continuum images* based on HMI science data. A line-of-sight magnetogram measures the flux of magnetic field as seen along the line of sight from HMI to the Sun. A continuum image is formed by filtering portions of the visible light part of the spectrum.
The line-of-sight magnetograms shows blobs of dark emission, and blobs of brighter emission. These correspond to opposite polarity magnetic fields breaking through the Sun’s photosphere. The magnetic field is important as it is related to the activity seen in layers of the Sun’s atmosphere such as the corona (which is observed by AIA). The continuum images allow us to track the evolution of sunspots. These images are important as they allow us to better understand the dynamic nature of the solar atmosphere.
The primary goal of the Helioseismic and Magnetic Imager (HMI) investigation is to study the origin of solar variability and to characterize and understand the Sun’s interior and the various components of magnetic activity. HMI makes measurements of the motion of the solar photosphere to study solar oscillations and measurements of the polarization in a specific spectral line to study all three spatial components of the photospheric magnetic field. HMI produces data to determine the interior sources and mechanisms of solar variability and how the physical processes inside the Sun are related to surface magnetic field and activity. It also produces data to enable estimates of the coronal magnetic field for studies of variability in the extended solar atmosphere, which is where the Earth is. Solar variability that affects the Earth is called “space weather”. HMI observations will help establish the relationships between internal dynamics and magnetic activity. In turn this will lead to better understanding of solar variability and its effects.
For much more information on HMI, please visit http://hmi.stanford.edu/. For more information on SDO, please visit http://sdo.gsfc.nasa.gov.
* HMI is a successor to the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). The Helioviewer Project has MDI line-of-sight magnetogram and continuum images going back to early 1996.
We recently changed the process of how we convert SDO-AIA science data into JPEG2000 images for use with the Helioviewer Project. The new process is now based on the scaling algorithms used to provide images for the Goddard Spaceflight Center’s SDO webpage. Images with the new scaling start from about 2011/01/31 02:00 – 04:00 UT onwards, depending on the measurement. The SDO-AIA 171 waveband shows the least difference between old and new scaling algorithms. All other wavebands show significant changes. We changed the scaling algorithms we use so that users are better able to see the structure and detail in these images without having to do any extra image processing themselves. We think the new images are a definite improvement, and we hope you like them too. Thanks to Leila Mays and Barbara Thompson of the SDO mission for their help in implementing the new scaling algorithms.
Around 2010/10/29-30 the SOHO spacecraft changed flight operations so it is no longer constantly aligned with the rotation axis of the Sun. SOHO now points to ecliptic north, which makes an approximate seven degree angle with the equator of the Sun. SOHO will still flip 180 degrees in order to maintain optimal communication with the Earth, but the rotation will now flip the spacecraft relative to ecliptic north. The raw image data that SOHO takes therefore shows the new orientation. At the Helioviewer Project, we rotate the data so that solar north is towards the top of your screen and the rotation axis of the Sun is vertical (i.e., parallel to the left and right hand side of a rectangular screen). Our science data processing software – JP2Gen – now takes account of the new rotation of SOHO and rotates SOHO science data appropriately. This is done to maintain homogeneity with the existing images we already provide, and makes it easy to compare images from multiple telescopes.
You may have noticed that we didn’t have any new AIA images, from about 2010/12/19. This was due to an interruption in the creation of the science-quality files we use to create the images available via the Helioviewer Project. The situation has been rectified, and we are currently filling in missing data between now and when the interruption began (approximately 2010/12/19 04:00 UT). We are filling in the missing data at the approximate rate of 1.5 – 2 days worth of AIA images per 24 hours.
We now have a completely independent machine producing SOHO JP2 files. Files made on that machine are transferred to our main server (and a reference copy is kept). This makes it easier to maintain a stream of SoHO images independent of the machines on which JP2Gen is developed. Now all we have to do is take care of the new orientation of SoHO…!
Many institutions host many different kinds of image data, either from observations or from simulations. I have put instructions on how to convert image data to a format the Helioviewer Project uses on our wiki page. The wiki is where we keep our must up-to-date instructions on the installation and use of all the software we are developing.
Contact me if you encounter any problem with the JP2Gen instructions , or with implementing JP2Gen on your local system (or any other part of the wiki). I’d be very happy to get your feedback!