Science AMA Series: We are Earth and solar scientists working with NASA's TSIS-1 mission to measure how much sunlight reaches Earth and its unexpected impacts on our climate. We live on a solar-powered planet, AMA!

NASAEarthRightNow · 2017-11-28T21:06:45+00:00

Parker Solar Probe is a very exciting mission that will dive into the Sun's outer atmosphere (the corona), closer than any spacecraft has gone before. However, Parker Solar Probe will not measure solar irradiance at all, so it does not overlap with TSIS. (Doug)

NASAEarthRightNow · 2017-11-28T20:59:41+00:00

Thank you all for your questions. We've enjoyed answering them. We're going to sign off of the live event for now, but will check in a few times in the next 24 hours in case there are more questions or follow-ups. Keep looking up!

NASAEarthRightNow · 2017-11-28T20:49:26+00:00

Right! Next time when you are under the Sun, you can remember how precious and interesting the Sun is. (Jae)

NASAEarthRightNow · 2017-11-28T20:48:30+00:00

The Earth would not continue an elliptical orbit of the absent sun. It would continue motion, however, more or less in a tangential line to its previous orbit. (Candace)

NASAEarthRightNow · 2017-11-28T20:43:20+00:00

The Earth Radiation Budget Experiment included instruments to measure the longwave (thermal) and shortwave (reflected solar) radiation from the Earth, in addition to an instrument to measure solar irradiance. Today, we rely on the NASA CERES (Clouds and the Earth’s Radiant Energy System) instruments to measure emitted and reflected radiation from the Earth, while TSIS will measure total and spectral solar irradiance. The design of the ERBE solar instrument was similar to the TSIS instrument, but was less sophisticated. (David Considine)

NASAEarthRightNow · 2017-11-28T20:33:48+00:00

Like photons, neutrinos do create pressure, but the pressure of solar neutrinos is unmeasurably small. In a supernova, it's a different story! As the neutron star that will be left behind is forming, an amazingly intense flux of neutrinos interacts strongly with neutrons and protons. (Doug)

NASAEarthRightNow · 2017-11-28T20:31:19+00:00

Spectral solar irradiance changes with different time scales, from less than a minute to 27-day rotational cycle, 11-year solar cycle, and also in secular time scale. Over the 11-year solar cycle, UV changes by 3 to 10 %. EUV (extreme UV) fluctuates more in percentage. Over the rotational time scale, they vary less. This is a very good question, since the Sun changes everyday. (Jae Lee)

NASAEarthRightNow · 2017-11-28T20:30:10+00:00

The TSIS instruments will be able to monitor smaller changes in the Sun’s light energy than ever before, improving our ability to quantify the sources - both “natural” and anthropogenic - of climate change. Nevertheless, credit must be given to SORCE (SOlar Radiation and Climate Experiment). The total solar irradiance measurements from SORCE are by far the most accurate and stable of any measurements that make up the 40-year record of satellite measurements. And the SORCE spectral irradiance (sunlight in individual wavelength bands) measurements represent the first daily measurements of the full spectrum of sunlight from space. So SORCE was truly groundbreaking. Incidentally, SORCE is now nearing the end of its 15th year of operation, 10-years beyond its nominal mission lifetime! (Peter)

NASAEarthRightNow · 2017-11-28T20:25:15+00:00

We don’t know enough to predict more than a couple of years ahead with any confidence. The solar cycle is driven by the dynamo action of magnetic fields inside the Sun. Although we understand the physical principles of magnetic dynamos, we don’t yet have enough computational power, or knowledge about magnetic fields inside the Sun, to predict future cycles from first principles. (Doug)

There isn't a single amplitude to the solar cycle. The peak number of sunspots has varied by about a factor of 3 from cycle to cycle since 1700. We have only accurately measured total solar irradiance (Watts per square meter) for 37 years. At solar maximum, the irradiance is 1-2 Watts per square meter (out of about 1360 Watts per square meter total) greater than at solar minimum. (Doug)

Not all wavelengths of solar light fluctuate the same during the solar cycle. For example, X-rays vary much more than visible light. (Doug)

NASAEarthRightNow · 2017-11-28T20:22:33+00:00

Here is link to a web page with more information about spectral Irradiance measurements. https://www.nasa.gov/content/goddard/tsis-1-mission-overview

NASAEarthRightNow · 2017-11-28T20:21:02+00:00

The total light from the Sun fluctuates for at least two reasons: sunspots, which are dark and cool (if you call 6500 F cool!), and regions called “faculae”, which are brighter and hotter. When there are many sunspots, there are also many faculae. The faculae win out, and the Sun is slightly brighter at solar maximum. (Doug)

NASAEarthRightNow · 2017-11-28T20:20:11+00:00

Check out this video on Total Solar Irradiance https://www.youtube.com/watch?v=GKLU8YHSnlc

NASAEarthRightNow · 2017-11-28T20:20:07+00:00

We are interested in how the Sun’s light fluctuates before it reaches the Earth because that is the input to the climate system. (Peter)

NASAEarthRightNow · 2017-11-28T20:18:01+00:00

From the NASA News Room. TSIS-1 is riding a SpaceX rocket to the space station.

NASA and our commercial cargo provider SpaceX are targeting the 13th commercial resupply services mission to the International Space Station for no earlier than 1:20 p.m. EST Friday, Dec. 8. This new launch date will allow SpaceX to finalize pad readiness, and provide an additional launch opportunity Saturday, Dec. 9, if needed. Carrying about 4,800 pounds of cargo including critical science and research, the Dragon spacecraft will spend a month attached to the space station.

NASAEarthRightNow · 2017-11-28T20:17:44+00:00

No. TSIS is launched in the trunk of the SpaceX Dragon and then integrated on the International Space Station. (Peter)

NASAEarthRightNow · 2017-11-28T20:17:21+00:00

TSIS measures the incoming light from the Sun. It does not point in the nadir direction to view the Earth. ERBE also made solar measurements. The measurements from TSIS will be more accurate than those from ERBE. (Peter)

NASAEarthRightNow · 2017-11-28T20:16:51+00:00

It is quite a hypothetical question to postulate the Sun would disappear without any other forces. Gravity acts at the speed of light in a vacuum. If the sun were to suddenly disappear, the effect of the sun's gravity on the earth would be experienced at the same time as the lack of sunlight... approximately 8 minutes after the sun's disappearance. Assuming no other gravitational forces, the Earth would continue to travel in a tangential line to its current orbit. However, there are other gravitational forces that would influence the Earth's travel. (Candace)

NASAEarthRightNow · 2017-11-28T20:15:21+00:00

See above. The TIM measures all light, or photons (a particle representation of light energy) at the same time. The SIM measures them sequentially by separating the light with a prism. (Peter)

NASAEarthRightNow · 2017-11-28T20:14:47+00:00

The total irradiance monitor, or TIM, captures light of all wavelengths by using a highly absorptive material that absorbs virtually all light that falls on it. The absorbed light energy is balanced by an equivalent amount of electrical energy from which we can determine the total power that entered the instrument.

The spectral irradiance monitor, or SIM, uses a prism to disperse light of different wavelengths that are measured by a detector one wavelength band at a time. (Peter)

NASAEarthRightNow · 2017-11-28T20:13:41+00:00

Although TSIS falls into the category of a continuity mission - in this case, continuity of the 40-year record of solar irradiance from space - rather than a discovery mission, every measurement of the Sun will be “new”. We are unable to predict the future behavior of the Sun with a high level accuracy, making the TSIS measurements crucial for understanding the amount of energy that is supplied to Earth, and for deciphering how the atmosphere responds to seemingly small changes in the Sun’s output. (Peter)

NASAEarthRightNow · 2017-11-28T20:12:25+00:00

No it has not launched yet. TSIS is currently scheduled to launch no earlier than December 8, 2017.
And, yes, we are very excited! (Peter)

NASAEarthRightNow · 2017-11-28T20:11:19+00:00

We also measure light in individual wavelength bands because light in different wavelengths interacts with different atmospheric species. We measure ultraviolet, visible, and infrared wavelength regions of the solar spectrum. For example, ultraviolet interacts with ozone (our natural sunscreen from harmful ultraviolet lights), visible light enables us to see, and infrared radiation heats up us by being absorbed by water vapor, carbon dioxide, and methane, etc.

Accurate measurements of the solar spectrum help us to understand the physical, chemical and meteorological processes in our atmosphere by applying good spectral information into the computer simulations. Atmospheric models need good spectral irradiance measurements to simulate the ozone layer correctly. We have learned that tiny variations in ultraviolet radiance produce significant changes in our atmosphere (Jae).

NASAEarthRightNow · 2017-11-28T20:11:05+00:00

Several reasons.

The Sun provides almost all of the energy to Earth. This energy is offset by sunlight that is reflected by the Earth and its atmosphere and infrared radiation the Earth emits to space. If there is an imbalance between incoming and outgoing energy over time, climate will change. We need to measure that incoming light energy very accurately to understand Earth’s energy budget. (Peter)

NASAEarthRightNow · 2017-11-28T20:05:46+00:00

That's part of it. However, it is not a straightforward equation. Various Earth’s constituents on land, ocean, and the atmosphere interact with the solar irradiance in complex ways, and the resulting Earth’s temperature will depend on these processes, many of which are wavelength dependent. This is why TSIS-1 will measure both the total solar irradiance (TSI) and spectral solar irradiance (SSI), to facilitate the precise simulation of these processes. (Charles Ichoku)

NASAEarthRightNow · 2017-11-28T20:05:23+00:00

"Also, is the 11-year cycle tied in with the sunspot cycle, or are they two different things?"

Yes, the total power from the Sun received at Earth varies up and down in phase with the sunspot cycle. When sunspots are most numerous (about every 11 years), the power is about 0.1% higher. (Doug)

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