Labor Day Weekend Aurora Borealis via VIIRS Day Night Band

September 6th, 2022 |

The recent 3-day weekend was a 3-night extravaganza for Aurora enthusiasts with an active Aurora Borealis lighting up the sky for 3 nights in a row.  The VIIRS (Visible Infrared Imaging Radiometer Suite) Day Night Band Sensor flying on the Suomi-NPP and NOAA-20 polar-orbiting satellites captured stunning snapshots of the celestial phenomena during each North America overpass.  

NOAA-20 VIIRS DNB image acquired in the early hours (0954 UTC) of September 3rd, 2022
Suomi-NPP VIIRS DNB image acquired in the early hours (0904 UTC) of September 3rd, 2022

Auroras are visible signatures of disturbances in Earth’s magnetosphere that occur when the solar wind interacts with Earth’s magnetic field during geomagnetic storms and substorms. They typically flow between 100 to 500 km above Earth’s surface. Polar-orbiting satellites fly at an altitude of 824 km (512 miles) and are perfectly situated to observe and monitor the Aurora Borealis in the Northern Hemisphere or Aurora Australis in the Southern Hemisphere.

Suomi-NPP VIIRS DNB image acquired in the early hours (1027 UTC) of September 4th, 2022
Suomi-NPP VIIRS DNB image acquired in the early hours (0845 UTC) of September 4th, 2022
NOAA-20 VIIRS DNB image acquired in the early hours (0704 UTC) of September 4th, 2022
NOAA-20 VIIRS DNB image acquired in the early hours (0935 UTC) of September 4th, 2022
NOAA-20 VIIRS DNB image acquired in the early hours (0753 UTC) of September 4th, 2022
NOAA-20 VIIRS DNB image acquired in the early hours (0614 UTC) of September 4th, 2022

Uniquely sensitive to low levels of visible light at night, VIIRS Day Night Band is the only satellite sensor able to detect and display the Aurora. The DNB is sensitive to radiation in wavelengths between 0.5 – 0.9 µm, which covers much of the visible and some near-infrared wavelengths. The images appear monochromatic because they are a combination of all energy within the entire bandwidth, meaning we can’t separate out the “green” or “red” parts of the data to see vibrant colors that citizen science photographers capture from below. Thousands of Northern Lights pictures were shared on social media over the weekend. Here are just a few …

Suomi-NPP VIIRS DNB image acquired in the early hours (0826 UTC) of September 5th, 2022
NOAA-20 VIIRS DNB image acquired in the early hours (0733 UTC) of September 5th, 2022

Day Night Band images from North America satellite overpasses are available via the VIIRS Imagery Viewer , a 7-day archive — refreshed daily — for all 22 VIIRS channels, usually within 60 minutes of being acquired onboard the spacecraft. Current and archived VIIRS images over the continental USA are also available on the VIIRS TODAY website. As future JPSS VIIRS satellites join the fleet, that data will also be available on these sites.

Of note: the JPSS-2 (NOAA-21) satellite is scheduled for launch on November 1st, 2022.

SAR Winds over the tropical Pacific Ocean

July 11th, 2022 |
GOES-17 ABI Band 13 (Clean Window Infrared, 10.3 µm), 0400-0510 UTC on 11 July 2022, along with SAR Wind observations at 0513 UTC (Click to enlarge)

This NOAA/NESDIS website shows small footprints where SAR observations of ice and wind (from the RADARSAT Constellation Mission — RCM — satellites and from Sentinel) are available. AWIPS-ready data are also available from an ftp site. Consider the animation of GOES-17 Band 13 imagery above, just south to the Equator, and to the west of 160oW longitude. The slightly cooler brightness temperatures at the eastern edge of the arc of clouds moving to the west is associated with two patches of strong surface winds. The toggle below zooms in on the region of winds. Surface wind speeds are close to 15 m s-1 with this weak line of tropical convection.

GOES_17 ABI Band 13 (Clean Window infrared, 10.3 µm) at 0510 UTC and RCM1 SAR Winds at 0513 UTC, 11 July 2022 (Click to enlarge)

Can Geostationary Imagers See Noctilucent Clouds?

June 20th, 2022 |

Q: Can geostationary imagers see the very thin, very high Noctilucent Clouds? A: Yes and no, depending on the satellite, how data are processed, time of the year, time of the day and spectral band. Thanks to Simon Proud for this tweet using JMA‘s Advanced Himawari Imager (AHI):

Note the very thin line near the top of the images on June 20, 2022. These images are derived from Japan’s AHI. A animated gif version.
A similar loop as above, but more zoomed in. From June 20, 2022. These images are derived from Japan’s AHI. An animated gif version.
A “spectral” loop of AHI’s three visible bands at 15 UTC on June 20, 2022. A animated gif version.

Since NOAA’s ABI is a similar instrument to AHI it seems likely that ABI can also observe noctilucent clouds at times. Noctilucent clouds are possibly only observable in visible bands when they are off the earth’s edge, with space as a background, and when illuminated from certain angles. However, due to ground system processing in the generation of the ABI radiance files, most users cannot see data that the ABI scans off the Earth’s edge in space. Special processing of ABI data does allow to show off Earth pixels, such as in these examples with the moon and the Webb Space Telescope plume in space. Recall that the AHI Full Disk is made up of 23 swaths (as opposed to 22 for the ABI), so it scans a bit more space both north and south of the Earth.

An animation including the AHI 3.9 micrometer band shows the relationship between the Earth’s edge and the apparent cloud location. (A animated gif version.) Consider also the large apparent displacement of these high altitude (“shining at night”) clouds due to parallax.

Also see this image:

GOES-2 Launch Anniversary; GOES Timelines

June 16th, 2022 |

With the help of NASA, private industry and others, NOAA’s GOES-2 (as GOES-B) was launched on June 16, 1977. Similar to SMS-1/2 and GOES-1/3, there were 2 spectral bands: one visible and one longwave infrared.

GOES-2 Visible (left) and Infrared (right) spectral bands from June 16, 1978 over the Eastern portion of the U.S.

A still image with a map overlay is also available to provide geo-referencing for the images in the above animation. Or a similar loop is also available with the map overlay The images in the loop (mp4 | animated gif) were taken just one year after GOES-B was launched.

A timeline of the GOES, from GOES-1 to GOES-U. Figure credit: GOES-R Program Office. (Click to show larger image.)
A timeline of the U.S. geo imaging, from ATS/SMS to GOES-U. Figure credit: GOES-R Program Office. (Click to show larger image.)

The timelines show the periods when the satellites were operational. Yet, there were other times when they might have been operating. For example, when an on-orbit spacecraft comes out of storage once a year, often in August, for a routine check-out of several weeks. Another example was GOES-14, as it provided over 5 months of 1 min data (SRSOR) data to better prepare for the meso-scale sectors on the ABI. These campaigns were in 2012, 2013, 2014, 2015 and 2016. Some of these times were:

Start DateEnd Date
16-Aug-201231-Oct-2012
13-Aug-201328-Aug-2013
08-May-201425-May-2014
14-Aug-201428-Aug-2014
18-May-201511-Jun-2015
10-Aug-201528-Aug-2015
01-Feb-201625-Feb-2016
18-Apr-201615-May-2016
09-Aug-201629-Aug-2016
01-Aug-201711-Aug-2017
08-Aug-201817-Aug-2018
31-Jul-201913-Aug-2019
11-Aug-202021-Aug-2020
11-Aug-202119-Aug-2021
GOES-14 times (as start/end pairs) of being operated, though not operational. All dates are approximate.

In addition, GOES-15 was operated several times to supplement GOES-17 operations:

Start DateEnd Date
20-May-201809-March-2020
04-Aug-202004-Sep-2020
04-Feb-202119-Feb-2021
02-Aug-202105-Nov-2021
17-Feb-202218-April-2022
GOES-15 times (as start/end pairs) of being operated, though not operational. All dates are approximate.

The second timeline above includes not only the U.S. GOES imagers, but also their precursors: ATS-1, 3 (including the Spin Scan Cloud Cameras) and 6 (with the 2-channel GVHRR; including an infrared band) and SMS-1/2. The GOES-R Program Office also has a more simple GOES timeline.

UW/SSEC has an interactive timeline (opens in new tab) that covers more satellites. The SSEC library (Schwerdtfeger) also has more information on the Spin-Scan Cloud Cameras on ATS-1/3.

Snapshot of the UW/SSEC timeline, the orange line relates to the geostationary orbit. (Click to better show image.)
A GOES-2 Full Disk image from June 16, 1978. The visible band is shown, along with cold IR values. (Click to show larger image.)

The above image shows a color-coded transparency for cold clouds over the gray-scale visible image.

After GOES-U, NOAA is planning on the next generation U.S. geostationary imager as part of the Geostationary Extended Observations (GeoXO) program.

H/T

Thanks to the many who made the GOES (and the precursors) possible. McIDAS-X software was used in generating these satellite images. The data (and many dates) was accessed by the UW/SSEC Data Services. More about GOES-16 and GOES-17 and GOES-18 (preliminary, non-operational).