This column is sponsored by ESRI

Remote sensing is a critical component of the geospatial toolset, particularly in this era of global impacts and global change. Remote sensing technologies enable us to bring together data on a global scale in order to study and analyze the intricate systems of our dynamic planet. Remote sensing will continue to increase in importance as our populations grow and our resources become scarcer.

The issue of sustainability is served well by the network of sensors that orbit our planet and send us calibrated and ongoing data about our resources, land use and impacts.

Global Coverage

I spent some time delving into the online chronology of scientific remote sensing satellites that’s maintained by Tag’s Broadcasting Services. The list dates back to the Launch of Landsat 1 in 1972, and includes details on each satellite, including country of origin, mission, launch vehicle, launch date and end of life if no longer operable.

The details presented here are a good resource, but may contain some gaps. For instance, it would be interesting if it also included all satellites that were launched that did not become fully operational. And it obviously doesn’t count classified military satellites that likely also return some scientific remote sensing data.

Perusing this list of spaceborne sensors shows that the 11 satellites launched last year is a record number in any given year. The pace of spaceborne instruments is also at an all-time high in this decade, with 62 satellites launched since 2000, compared with 59 in the 1990s, 32 in the 1980s and 17 in the 1970s.

An increasing number of countries are also involved in remote sensing efforts. There are now well more than a dozen countries with satellites, including the United States, Russia, China, Canada, Israel, Italy, France, Egypt, Japan, India, Indonesia, Brazil, Argentina, Algeria, Nigeria, Morocco, South Korea, Turkey, Taiwan, the United Kingdom, Ukraine and the European Union.

The pace of remote sensing satellite launches will only increase as we realize the need to gain a better understanding on our dynamic planet. Remote sensing satellites provide an extremely valuable and unique scientific perspective, with the ability to cover wide areas to uncover broad change over time.

Many Types of Sensors

There are many different types of airborne sensing instruments at many different resolutions. For many purposes these days we’re looking for the greatest possible spatial resolution for our imagery so that even small features on the ground can be seen clearly and classified from space. The smallest current resolution of a spaceborne remote sensing satellite is under one meter resolution, but there’s continued use of satellite data at 30 meter resolution for broad landscape study.

Spatial resolution isn’t the only consideration for a sensors capabilities. Spectral resolution relates to the different wavelengths of light that the sensor can record. Temporal resolution refers to the amount of time it takes between visits by the satellite to the same geography. For instance, it takes the Landsat satellite 16 days to revisit the same spot on Earth. There’s also radiometric resolution, which refers to the brightness values in each band of information. Each of these resolutions can be fine tuned for specific purposes.

In addition to imagery that can be viewed and calculated, there are airborne instruments that are able to detect moisture, chemical composition and the health of vegetation. Remote sensing is applied to geologic application, agriculture, forestry, ecology, urban land use, mineral and petroleum exploration and other tasks.

I’m quite certain that we’ll continue to advance sensing technologies to detect many more inputs at higher resolutions. Today’s applications provide an impressive array of measurements that are extremely valuable to scientific study. Future scientists will have an increasing number of sensors and measurements to study, with sensors that continue to adapt to the needs of the missions. Individual sensor inputs as well as multi-sensor arrays will gain orbit to provide valuable top-down data.

Interconnected Measurements

The idea of an integrated sensor web of instruments that speak to each other and communicate with ground-based sensors continues to intrigue me. I wrote about this topic in a previous Perspectives post. The combination of space and ground-based measurements in real-time, with software tools that can model these measurements in an adaptive and integrated way, could shed incredible insight into the complexities of our planet.

Collaboration between countries that own the satellites is very important in order to realize the promise of these tools. The data should be shared with scientists from around the world and the scientists themselves must cooperate and collaborate with scientists from many nations in order to analyze the resulting data for optimum understanding.

The current decadal growth of remote sensing satellites is roughly 50% growth per decade. I’m certain we’ll see this number maintain and accelerate as countries realize the need to closely monitor their land mass for economic and ecological security, in addition to political security.

Read what Jeff Thurston has to say on this topic here.

References

Eyes in the Sky Track Earth’s Changes, SCIENTIFIC AMERICAN
Remote Sensing Satellites, Website with chronology and details on satellites in orbit
Technical and Historical Perspectives of Remote Sensing, Nicholas M. Short, primary author
Remote Sensing Resolution, James Madison University

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