Meeting Minutes - OST STDT Bi-Weekly Telecon - February 9, 2018


Subject:OST STDT Bi-Weekly TeleconDate:2/9/2018
Purpose:To discuss science activities for OST.Facilitator:Asantha Cooray
Location/Time:

Telecon: WebEx Online

Meeting Number:

+1-855-749-4750 US TOLL FREE

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Access code: 194 170 917

Note Taker:Sydney Jones

Discussion Items 

Review Science Requirements 

  • Exercise is to make three science goals parallel with three themes. The three science goals are:
    • Are we alone? 
    • How did we get here? 
    • How does the universe work?
  • Need to reach science goals in one year, which also needs to be included the report. 
  • This is for the purpose of writing the report. The paper will include ancillary stuff such as tables and figures.
  • @Tiffany M. added that we need to be careful about what three science goals will be promoted throughout the study.
    • Three themes will be based on science goals. 
  • Cara Battersby suggested that we brainstorm science priorities and check in with the science community as well. 
  • Instrument exercises are occurring at Goddard in April. Margaret Meixner indicated that exercises are already mid-stream.
  • Thomas L. Roellig added that by COB on  there were demands for what the science priorities would be with some of the instruments. We will say we will descope the size of instruments this is how we lop things off, and would get a big bang for our buck. As far as the earlier rankings go it shouldn't be that painful. In re-prioritizing and working on instrument design, if we wait too long we may design the wrong instrument.
  • Margaret Meixner added that things are already mid stream in terms of the instrument design. In April, OSS will be doing serious engineering work. Matt Bradford needs whatever specifications now. Can base this on programs we have now. Reshaping and pitching the science case can take longer. We are baselining things with instrument prioritization but also the rankings from June. Should proceed with this and do this in parallel with the exercise. 
  • Thomas L. Roellig encouraged science working group and team leads to let the teams know if they are going down the wrong path, or reaffirm with the team that they are doing well (if they are) which would give them more confidence in laying out the path as they design. The leads will be getting best guesses from instrument teams of what the skinnier instruments will look like.
  • Kartik J. Sheth suggested that Thomas L. Roellig give an example of what he means that drives the requirements instead of just reinforcing science prioritization. 
    • Thomas L. Roellig responded that all space missions (Spitzer, JWST, or explorer class mission) have to develop science drivers and goals and drivers  which are the are boiled down prioritization, where you answer a specific question and need to have measurement capabilities in order to do it. Once this is done, one can then figure out how to design something to make those measurements. Sometimes you realize science goals have to be revisited.  
    • Kartik J. Sheth added an example for ALMA and its driving requirement. 
    • Thomas L. Roellig added that we are starting with the June 2017 ranking. He hopes that we are doing a basic repackaging and not a serious re-prioritizing, or else we may be in trouble. 
    • Asantha Cooray indicated that there is no re-prioritization, it is a re-phasement of how we .want to restate science goals as top objectives and making sure we can do them in a reasonable amount of time. 
  • Theme Discussion
    • THEME: Are we alone? (Exoplanets, transit and direct imaging) - SEE Kevin Stevenson's POWERPOINT PRESENTATION FOR SPECIFIC SCIENTIFIC DETAILS
      • Kevin Stevenson added that he was asked to address the question are we alone? The general questions we are trying to address are two fold. 
      • The transiting exoplanet science case may be along the lines of what fraction of habitable zone planets orbiting m dwarfs...at this point of life.
      • Direct imaging science case may be what occurrence rate of sat urn mass or larger exoplanets and how they evolve over the first...years of time. 
      • Kevin Stevenson will talk about both of these science cases in the context of concept. Tiffany Kataria helped Kevin Stevenson with transiting exoplanet case. @Tiffany Meshkat helped him with the direct imaging science case.
      • MISC instrument functions: similar to Concept 1, 5-25 microns and an evolution of 100-300. Ran six simulations to address the question and determining the impact assuming the different noise floors. Noise floor was unknown for Concept 2. Looked at 10, 5 and 0 ppm on noise floor, looking at number of visits from 30-100. We are detecting bio-signatures for ozone and methane. 
      • Ozone
        • 40 ppm feature size. 
        • Noise floors do not effect detection significance of ozone, CO2 is easier to detect. 
          • Thomas L. Roellig added that for a 3.5 sigma is not extraordinary enough. 5 sigma would have been a good criterion.
          • Kevin Stevenson added that five sigma is a good detection threshold. The table indicates that 30 visits does not have a big impact on the noise floor. 
          • At 100 visits (what we are leaning towards for final 3 or 4 planets that we have high confidence in) we will have 5 sigma detection regardless of the noise floor. At 10 ppm we can still get a 4.9 sigma detection of ozone. The limiting factor is methane. At 100 visits depending on the noise floor we can have 3, 4 or 5 sigma detection, assuming a 20 ppm methane feature size. It is difficult to say how strong methane feature will be in transmission around m-dwarfs. We need methane and ozone. 
          • Gary Melnick asked what do you think will be measured in mid 2030-2040,  based on decades of extremely large telescope. Will it be possible to narrow the width of the targets, based on telescope observations planned in the next decade. 
            • Kevin Stevenson responded and indicated that JWST  and some ground based telescopes will determine whether or not a planet will have an atmosphere. Trapis planets masses were revised, new masses show that they do have atmospheres full of water. They wont be able to claim biosignatures, but can constrain what planets are the best ones to look at. 
            • Kartik J. Sheth asked if the MISC will get the full spectrum from 5-20 microns in the current design. Effectively if we saw ozone detection and maybe nominal pH 4 detection, in 30 orbits we could for another 20 orbits. 
            • What is the expectation from tess, and how many stars would we be able to see? We are expecting k of 8 to be optimistic and range between 8 and 12, for objects within 15 parsecs. This was simulated in the diagrams to see how many parsecs can be observed in a given amount of time, In this case, telescope diameter is the Y axis and program time on X axis. For the best 20 targets we can make a 5 sigma detection of cO2 in atmospheres. In picking best 20 targets, some may be 7, 8 or 10, 11 or 12 magnitude. We can then detect which ones have atmospheres, cO2 features, and right temperatures for habitability. We can condense this down to the best 5 or 10 targets and emphasize telescope time. 
        • With ozone at 2,000 hours we can constrain ozone in 14 of those planets. This process can be done for methane and water. 
        • Asantha Cooray added that we also need ozone and methane, and need to justify how many planets we can detect. We can get a limit on the fraction (at 20) we can make a reasonable determination. 
        • The 2,000 hours is straight integration time, pure science. This is either equal in out of transit time or double. Kevin Stevenson will verify this in his notes. 
        • Gary Melnick asked what the smaller version of LUVOIR is claiming for number of planets to get significant results? It may be a half dozen. 
        • Matt Bradford added that 2,000 hours is over all 20 stars (100 hours per). Does the actual scheduling make sense and could it be accomplished in a two year period. On average, you may get 15 transit events per year per target over a two year time span. You could get 15 transits and 15 eclipses in which case you can go one year. 
        • Tess will find a few m-dwarfs. We anticipate ground based such as Trappist, to find all planets orbiting m-dwrafs in 15 parsecs. 
        • Johannes Staguhn asked about feature of infrared for two microns? Methane detection can be done in the mid-IR (possibly by JWST, but they dont have the precision). 
      • CONCLUSION: Asantha Cooray added that the two things coming out of this are 1) Doing better than 10 ppm 2) Out of R of 50. 
        • Kevin Stevenson indicated that we've selected R of 100. 
        • R of 300 is necessary for water at 18-25 microns. There will be a variation of R. Two water channel will have R of 300.
        • Run into trouble when looking at methane. 
      • THEME: Direct Imaging 
        • Motivation for this case is exoplanet formation and evolution. 
        • Determine the occurrence.....of gas giants down to Saturn masses and trace evolution of planet formation to first billion years afterwards.
        • Measurements are complimentary to what can be done with RV and transit measurements. 
        • Phase space is 10-50 au range for typical near by system. 
        • Gary Melnick asked if exoplanet system architectures are a motivation (wide variation of planets being close to their stars, direct imaging would help to detect planets in the outer parts of the system)?
          • Planet migration is something to consider. Near cam observations can look at systems up to the first hundred million years. Tiffany Meshkat can confirm this.
          • JWST will have near cam and miri coronoraphy, they have 4 filters and contrast ratio is 10 to the minus 3. 
          • WFIRST will have coronograph in the optical wavelength range. 
          • OST must beat tWSTs  contract ration in the wavelength range. Most observations are looking at jupiter mass and larger objects. We can expect that Saturn mass planets are more common than Jupiter mass planets in the solar system. 
        • Contrast ratio is better in the mid-IR than other wavelength regions. 
        • Thermal emission does not have a dependent on orbital phase which is a huge problem for reflected light direct imaging. 
        • OST will be able to determine current...rate of Saturn mass and larger objects at 10 + au in the first billion years. 
        • Asantha Cooray can we make the estimate that given a certain number of program hours a certain number of Saturn masses can be detected? 
          • Tiffany Meshkat added that these measurements will be observed in the optical with reflected light. Pushing down lower contrast can probe radial velocity planets. Since we are probing a phase space of planets that's unprobed, we can try to come up with a number, but can not easily say that we know the brightness of these known planets and the number of the planets. 
          • Asantha Cooray indicated that JPL may have a code making predicitions for LUVIOR and HabEx. Kartik J. Sheth added that mid-IR is not integrated in to Chris Starks work and exoplanet standards team. Onis is on OST to find this out (Eric Neilson was the POC for this). Need to touch base wilth Eric Neilson on this. Kevin Stevenson will follow up with Eric Neilson on this.
        • Coronograph can be used for imaging. It doesnt have to drive science requirements. Can use this in the mid-IR and achieve contrast ratios better than MIRI, to address science questions that other missions cant, in
          • Expanding targets by a factor of ten by going out to one billion years in age and pushing down to Satrun mass objects, We have a strong science case that doesn't have to drive science requirements.
          • Itsuki Sakon added that we are checking on how much contrast can be achieved from the instrument point of view. 10 to the minus 5 is challenging.
          • Thomas L. Roellig we don't need spectra. Would one wavelength be sufficient?
            • @Tiffany Meshkat added that we havent evaluated this completely.
          • David Leisawitz how does this coronograph compare with JWST MIRI coronagraph and capability? Thomas L. Roellig is not sure. Asantha Cooray added that MIRI is 10 to the minus 3, 10 to the minus 4. The requirement of 10 to the minus 5 is ten times better, however; this may be challenging. 
          • Itsuki Sakon indicated that having a deformable/tip tilt mirror would help to achieve better capabilities than JWST. The telescope design's mirrior shape is complicated. We must examine how much improvement is achieved in the case of JWST. It will take a while to get this numner. 
            • David Leisawitz indicated that we would be able to calculate once we know the observatories performance and jitter to compare this with JWST MIRI. 
            • Tiffany Kataria reinterated the write up that she sent out (including Tiffany Meshkats input) addresses some of these concerns.
        • CONCLUSION: Can we gain or beat JWST in terms of imaging with a 5.8 meter telescope. 
      • THEME: Trail of water - SEE Gary Melnick's POWERPOINT PRESENTATION FOR MORE INFORMATION. 
        • Presented slide showing water transitions with energies above the ground state between 50, 100 and 150 K. Showing beginnign of water trail starting with clouds that are cold. Top panel has energy above ground state of less than 27 Kelvin (k). The point of this slide is that all of these would fall in wavelength range of HERO and ....instrument.
        • Next slide shows transitions excited to 150 K. They both are tranisitioned to the lowest ortho line level. The 557 gigahertz line is lower than the 1670 gigahertz line, difference being energy above the groundstate of 27 K versus 80 K. 
        • The next slide shows spectra from Herschel high pi instrument.  The 557 gigahertz line is important because it is the lowest line transition of most abundant form of water (ortho water) quite advantageous to have access to this line in terms of detecting weak emission towards cold sources in prestellar phase. Hard to argue that OST is required to do CO, but by virtue of larger aperature, will be more sensitive by a factor of seven than you can do with SOFIA. 
        • Next slide shows important species in understanding water (HDO). Gary Melnick has not plumbed the depths of the argument for why these transitions are particularly important, for ALMA or of he ground based radio telescopes. HDO case is limited by the fact that you can do these transitions from the ground, its the comets. This case is best centered around the comets. OST can win by arguing that this can be done simultaneously (having access to this line). Asantha Cooray added that we should think in terms of water when writing this case. Comment from Paul Goldsmith:  you need accurate ratios of HDO/H218O as well as other isotopic ratios.  To do that you need similar beam sizes and good calibrations.  The H218O can be done with difficulty from SOFIA but you need to have much higher sensitivity to get a real sample of comets as they show considerable variation.
        • HDO should be included. 
        • Last slide shows the transitions above 550 gigahertz and energy above the ground states. We a probing 30 and couple 100 K with these transitions. These are useful but may not be exclusive to OST.
        • Asantha Cooray suggestied action to Kevin Stevenson: need program where we can talk about how to showi the targets we can do how many sqaure degrees and integration time. Suggested doing calculations to include in the report.
        • Is the heterodyne instrument present or not? There will be a heterodyne instrument but it will not look like Concept 1. 
        • Margaret Meixner indicated that we are using the June 2017 ranking. 


Action Items 

No.Action Item(s)OwnerTarget Due DateStatus (In progress/Completed)
1Instrument Prioritization Poll: Send out survey monkey or vote on FIP being 3rd (Thomas L. Roellig indicated to make sure to include whether it's a wash to avoid any conflict) 

Margaret Meixner

Asantha Cooray

 In Progress 
2Assemble more information on the JWST comparison, and send something around to STDT (the spreadsheet that Carter summarized)Ruth Carter In Progress