Image from TERRA
Fri, 17 Aug 2018 13:56 EDT

NASA's Terra satellite looked at water vapor and cloud top temperatures when it passed over the recently strengthened Typhoon Soulik in the Northwestern Pacific Ocean.

Image from TERRA
Mon, 13 Aug 2018 14:29 EDT

The largest fire in California's history, the Mendocino Complex, is still spewing clouds of smoke across the state.

Image from TERRA
Mon, 13 Aug 2018 12:38 EDT

After Tropical Storm Yagi made landfall in China, NASA's Aqua satellite saw the storm was moving inland and dropping heavy rainfall.

Tag: data

ASTER First Light After Safe Hold

ASTER First Light After Safe Hold

Image credit: NASA/GSFC/METI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team.

Terra and its sensors are back on line and collecting data.  The ASTER team released this first light image. The area is in Queensland, Australia where the Elliott River meets the Pacific Ocean. To the south of the river is the Burrum Coast National Park, appearing deep red. The brighter red areas to the east of the National Park is farmland. North of the River is the small town of Elliott Heads with a population of less than 900 people.

Congratulations, ESA on the Launch of Sentinel 3A!

Sentinel-3A, the European Space Agency (ESA) – developed Earth observing satellite successfully launched on February 16, 2016. Sentinel-3A is part of Europe’s Copernicus environment program and carries four sensors: The Sea and Land Surface Temperature Radiometer (SLSTR), the Ocean Land Colour Instrument (OLCI), the Synthetic Aperture Radar (SAR) Altimeter, and the microwave radiometer.

Researchers who use Terra MODIS data are particularly interested in OLCI. OLCI images the earth similarly to MODIS on NASA’s Terra and Aqua satellites. It measures specific ocean color, vegetation and atmospheric measurements at 300m spatial resolution and at 1270 km swath width. Sentinel 3A has a morning crossing time like Terra, making Sentinel-3A the most similar to Terra satellite currently flying. Like MODIS data, Sentinel data will be free of charge and provided worldwide.

Congratulations, ESA!

ESA: Sentinel and the Copernicus program

Ralph Kahn: “The Stories Data Tell.”

February 1, 2016

Headshot of Ralph KahnNASA climate scientist Ralph Kahn presented a Maniac lecture at Goddard Space Flight Center entitled, “The Stories Data Tell.” At an early age, Ralph found that separating causality from coincidence can be the lynchpin of understanding, and at times can help identify prerogatives or highlight the path toward the better options. Ralph shared his experiences, professional, personal, and at the intersection of the two, where the difference seemed to matter. And how data can help address this challenge, providing evidence one way or the other – sometimes!

Ralph Kahn, a Senior Research Scientist at NASA’s Goddard Space Flight Center, received his PhD in applied physics from Harvard University. He spent 20 years as a Research Scientist and Senior Research Scientist at the Jet Propulsion Laboratory, where he studied climate change on Earth and Mars, and also led the Earth & Planetary Atmospheres Research Element. Kahn is Aerosol Scientist for the NASA Earth Observing System’s Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA’s Terra satellite. He focuses on using MISR’s unique observations, combined with other data and numerical models, to learn about wildfire smoke, desert dust, volcano and air pollution particles, and to apply the results to regional and global climate-change questions. Kahn has lectured on Climate Change and atmospheric physics at UCLA, Caltech and many other venues, and is editor and founder of PUMAS, the on-line journal of science and math examples for pre-college education.

NASA Features from AGU: Terra

The American Geophysical Union recently concluded its Fall meeting in San Fransisco, California from December 14 – 18, 2015.  As part of the meeting contributions to science were featured on  Data from Terra’s instruments played important roles in collecting data to further research in each of these featured areas.  Read the full features from available at the links below.

El Niño

NASA: Observing the 2015 El Niño – The strongest El Niño since 1997 – 1998 is being monitored for the first time by a host of satellites, including Terra. This video (above) features global data sets from Terra’s instruments and their contribution to El Niño research.

How NASA Sees El Niño Effects From Space – The Moderate Imaging Spectroradiometer (MODIS) contributes to data collection on fires and hurricane monitoring

NASA Examines Global Impact of the 2015 El Niño – El Niño research pulls from data from Terra’s 16 years of data collection, monitoring Earth’s systems from Space

Warming Lakes
Study Shows Climate Change Rapidly Warming World’s Lakes – The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) contributed to this study.

Studies of Recent and Ancient Nepal Quakes Yield Surprises – The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) contributed to this study.

Sensor Degradation Leads to Calibration Improvements

Changes in the MODIS sensor, not dark ice led scientists to incorrectly determine that the Greenland ice Sheet in the Arctic was darkening. These results and others led to improved calibration corrections in the Collection 6 reprocessing of Moderate Imaging Spectroradiometer (MODIS) data.

A recent study suggested that sensor degradation of the MODIS instrument on NASA’s Terra satellite was responsible for the incorrect data. Ironically, the high quality of the MODIS sensor is what initially led Arctic scientists to look for a subtle change in ice brightness. The data collected by MODIS led researchers to consider that the Greenland ice sheet was darkening from an increase in dark aerosol deposition on the snow. However, ground based measurements showed that there had been little if any change in the color of snow.

Ice darkening could have had big implications for climate researchers. Just like black asphalt absorbs radiation from the sun, resulting in a warmer surface temperature, the darkening of the ice sheet could warm the surface temperature around the snow, increasing snowmelt. This could result a shrinking Greenland ice sheet and have implications on sea level rise.

The combination of a well-understood sensor, high-quality analysis of the satellite data, and coordinated measurements at the surface led to the conclusion that a sensor artifact, a change to an image from defects or degradation of optics, was the culprit this time.

Satellites, like many scientific instruments, need to be calibrated to be able to maintain accuracy. If you’ve ever stepped on a scale and gotten a number that was far too high or too low to be accurate, you’ve been a witness to the degradation of an instrument. Scales can be fixed easily by taring, or resetting the instrument to zero when nothing is being weighed.

Fixing satellite sensor degradation, isn’t quite as easy, but is common practice. The complexity of an instrument like MODIS makes the calibration process much more difficult. Often, there are small instrument effects that are not obvious until many years of data from multiple applications indicate an issue. The dark ice example is one such case.

The vigilance of the MODIS scientists and those working with the instrument calibration led to five previous reprocessings with the sixth currently underway.. Each time the data is reprocessed, degradation of the instruments are taken into account and the data is calibrated based on data collected from other sensors on other satellites as well as from data collected on Earth. MODIS is on-board both Terra and Aqua, when data from these sensors don’t match up the data can be corrected based on data gathered on Earth.

While it may be easy to assume that an aging instrument may be less accurate, in reality the longer the data record that it collects, the more accurate the data can be through reprocessing. Just think, if Terra had only lasted it’s six year design life, instead of going on 16, this error in the data may never have been caught and accounted for in newer data collections.

Thus, while the dark ice example could be considered by some as an indication of a flaw in how satellite data are used, it is, in reality, a success story for how a community of scientists working with groups like the MODIS Characterization and Support Team are striving to get to the right answer.


Sun, J., X. Xiong, A. Angal, H. Chen, A. Wu, and X. Geng, (2014) Time-Dependent Response Versus Scan Angle for MODIS Reflective Solar Bands,IEEE Transactions on Geoscience and Remote Sensing, 52 (6), 3159-3174.

Polashenski, C. M., J. E. Dibb, M. G. Flanner, J. Y. Chen, Z. R. Courville, A. M. Lai, J. J. Schauer, M. M. Shafer, and M. Bergin (2015), Neither dust nor black carbon causing apparent albedo decline in Greenland’s dry snow zone: Implications for MODIS C5 surface reflectance, Geophysical Research Letters, 42.

Atmospheric science: Arctic snow is not becoming dirtier. (2015, 29 October). Nature Research Highlights, Accessed November 25, 2015.