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I've been reading a few things about NOAA's GOES-R satellite, and I noticed this on the GOES-R site:

...will be placed in the 89.5° checkout orbit where it will undergo an extended checkout and validation phase of approximately one year.

What are they doing in that validation to take a full year? It seems like they could make sure it's working a lot faster than that.

Also, it looks like future launches for other GOES satellites won't take as long for that part of the process. I haven't yet found exact timelines for GOES-S, GOES-T, and GOES-U, but their test phase isn't nearly as long as GOES-R. Why not?

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    $\begingroup$ Good question! Wild guess would be to cross-check with other satellite and ground truth data sets the various new technologies used by GOES-R throughout a full cycle of meteorological extremes known to Earthlings as "weather", before deploying similar systems? Or maybe to keep some data under wraps until some nice papers can be published? Or to make sure everything is understood before making enhanced emergency weather warnings based on the new technologies? Predicting the weather isn't rocket science, it's harder! $\endgroup$
    – uhoh
    Nov 20, 2016 at 8:21

2 Answers 2

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There are two questions in this question. I'll answer the second question first because (a) this second question is easier to answer, and (b) the answer to this question leads to the answer to the key question. The second question:

I haven't yet found exact timelines for GOES-S, GOES-T, and GOES-U, but their test phase isn't nearly as long as GOES-R. Why not?

GOES-S, -T, and -U are intended to be exact duplicates of GOES-R. They will have the same sensors and the same operational processes as will GOES-R. Intents are one thing, reality is another. The sensors on the follow-on satellites will inherently differ slightly from those on GOES-R. The validation period for those follow-on satellites will address the slight differences between those satellites and the already validated GOES-R.

The validation period for those follow-on satellites will not address the complex ground processes that transform the raw data transmitted by the satellite to Level 1A, Level 1B, and Level 2 products. Those processes will already have been validated by the time those follow-on satellites are launched. That will take considerably less time than will the validation effort for GOES-R.

Now the key question:

Why will GOES-R take a whole year for validation?

This is primarily because GOES-R essentially is a brand new instrument. The goal is to reach what's called "provisional status" within six months after launch. This means that all of the processes that transform the raw downlink to Level 1A products to Level 1B products to Level 2 products are functioning correcting, and that the underlying science in those transformations is basically correct.

There are several key challenges here:

  1. Are the scientific instruments measuring what the scientists think they are measuring?
  2. Is the processing from raw data to Level 1A products correct?
  3. Is the processing from Level 1A to Level 1B products correct?
  4. Is the processing from Level 1B to Level 2 products correct?
  5. Can all of that required processing keep up with the much increased volume of data transmitted by the satellite?
  6. Do those Level 2 products agree with alternative observations of the same effect?

There are a lot of ways things can go wrong in the above. The instruments themselves might have problems, the underlying science might have problems, and the complex software that performs the transformations from raw data to derived products might have problems. The system has to function properly, end-to-end, and the derived products have to agree with already validated (but perhaps localized) alternative measures of assessing those derived products.

The goal is to have the system at provisional status within six months after launch. That's not quite good enough. Having the system achieve operational status and have the products compare favorably year-round with validation data will take another six to nine months.

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    $\begingroup$ As an aside, I was personally involved early in my career in two major effups regarding those points I raised. My first job out of college was to document the supposedly complete Level 1B processing for the Nimbus-7 SBUV/TOMS experiment. The entire programming team had left for other jobs because they were done. They had a chest high stack of computer printouts to prove this. I spent a few of weeks learning FORTRAN and then delved into their code and test results. Back in those days, when a program dropped core, the computer printed the entire program, in hexadecimal (continued). $\endgroup$
    – David Hammen
    Nov 20, 2016 at 17:13
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    $\begingroup$ Those core dumps (abend dumps back then) were their test results. Nothing worked; their software was pure excrement. I was supposed to be a junior programmer, but I quickly proved myself to be more than that. The company hired a new senior programmer, who was excellent, and a new midlevel programmer, who was quite bad. The senior programmer and I rewrote the entire system in less than a year. We let the midlevel programmer do what he did best, which was not much. (continued) $\endgroup$
    – David Hammen
    Nov 20, 2016 at 17:19
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    $\begingroup$ We two rewrote the system, resulting in considerable local acclaim for the two of us. I was offered multiple jobs within that contractor. Having a science background, I wanted to do science. I was assigned to work directly with the principal investigator. The PI, along with the rest of the scientific team, did not their good scientific names sullied by suspect data. I was asked to come up with a scheme that rejected suspect data. The biggest problem lay with low backscatter angle data. (continued) $\endgroup$
    – David Hammen
    Nov 20, 2016 at 17:36
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    $\begingroup$ My code marked suspect ozone levels involving the low backscatter angles as missing. I initially argued against that, but the team was adamant. I argued for having two products, one for NASA-only use and the other for public dissemination. The team remained adamant. There would only be one product. My name was all over the code that resulted in NASA not being the first to observe the ozone hole over Antarctica. That fame instead went to a British scientist who used a relatively cheap handheld Dobsonmeter. (continued) $\endgroup$
    – David Hammen
    Nov 20, 2016 at 17:40
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    $\begingroup$ Almost a decade after I wrote that code, very high level NASA management managed to find me, despite four job changes and a move to Texas (I had been infected with the highly contagious human spaceflight virus). NASA seriously wanted to know whether I was a traitor (seriously!). This has been noted as one of "ten historical software bugs with extreme consequences". (continued) $\endgroup$
    – David Hammen
    Nov 20, 2016 at 17:45
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Let me add a few other points on top of David's already excellent answer. There are some other fixed timeframes that occur after launch but before the Satellite can become operational:

  • Orbit-raising: It will take GOES-R about 2 weeks to get to geostationary orbit.
  • Outgassing: It can take quite a while for all of the atmospheric gasses that "hitchhiked" in the satellite to be dispersed, to enable all the instruments to operate properly.

The above items will be, of course, common to all the launches (R, S, T, U). Additionally, the GOES-R satellite series includes new products and instruments, not yet flown on earlier GOES missions. So, in addition to testing the ABI imager and Ground Station software's ability to process the data from the imager at higher resolutions, as David mentioned, there are three times as many spectral channels to check-out. Also, there are some brand-new instruments on GOES-R, such as the GLM (Geostationary Lightning Mapper), that the ground team could only test using simulated data (instead of, for example, scaling GOES-NOP data to use as test data) up to this point.

Here's a nice publicly accessible document that goes into more of the details of what is planned for testing: Post Launch Calibration and Testing of the Advanced Baseline Imager on the GOES-R Satellite.

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