Iannis Dandouras , Henri Reme , Peter Wurz , Francois Leblanc , Eric Quemerais , Nikolaos Paschalidis , Lynn Kistler , Andrew Fazakerley , Rumi Nakamura , Benjamin Grison , Jean-Louis PINCON , Johan De Keyser , Sylvain Ranvier , Martin Wieser , Esa Kallio , Octav Marghitu , Ioannis Daglis , Yoshufumi Saito , Takeshi Sakanoi , Jorg-Micha Jahn , George Parks , John Sample ---------------- Dear NITRO team members. Iannis, Eric, and myself attended the M4 interview at ESTEC, giving 30 min presentation and 30 question/answers. The presentation itself went smooth, while there are several tough questions. We tried to answer as best as possible, but I found we could have added to the answer as marked by ***. One thing we did not expect was that there are many questions about the observation quality and sciences for the one-spacecraft option (e.g., NUVO resolution and return-flow assessment). %<< After finishing the interview, I looked back our proposal, and realized that Remote sensing spacecraft does not have so many European instruments. So I wonder the review panel and/or ESA consider one-spacecraft option as first hand. This is what we did not consider in answering the question last week. Now, we need to start pinpointing how much science can be done with one-spacecraft compared to the two spacecraft. This will be immediately needed if NITRO goes phase-A, and this is anyway needed to consider in the future even if the NITRO would not be selected. Therefore, I feel small strategic mistake, but we will see how the review panel decide in June. %>> Yama ------------------- Questions from review panel. (1) Is the current value of escape rate 10^24 /s (one of the article) correct? => Our answer: No measurements exist, and considering the large variation, it should be somewhere between 10^24/s and 10^26/s. (2) How much chance of total escape to reach 5x10^18 kg (average of 10^27/s rate)? => Our answer: Key point is the duration of high escape rate and not the current escape rate. Therefore, we have a good chance. *** I should have examined large events (like halloween event) when we can measure the highest escape rate of oxygen. If it reaches 10^28/s instantaneously, we could have make our argument stronger. *** We should have added a statement/viewgraph of the science consequence when the escape rate is low (e.g., we can say that Nitrogen inventory did not change very much, and the Earth-Venus difference comes from 4 billion years ago, or like that). (3) At Mars, if one look at N/C ratio and N/Ar ratio, it is as much as 10% of the Earth (not like 0.01% compared to oxygen). Then this can be explained by jeans and hydrodynamic escape during the early planet history and Martian nitrogen is not longer the mystery. => Our answer: This escape rate is related to 15N/14N difference, and argument the above explanation will be questioned if the nitrogen escape from the Earth is huge. *** I could have also mentioned Venus because the panel members comment is no longer valid if we apply the same concept to Venus. The available model that explains both the Earth and Mars does not explain Venus nitrogen according to my knowledge, and the available model that explains both the Earth and Venus does not explain Mars. *** We could have asked modeling people for a simple numerical calculation assuming different escape between isotopes and between different escape mechanisms. (4a) The mission does not measure the return flux. => Our answer: Our mission covers a closed sphere and all the key regions for escape (polar cap) and return flux (inner magnetosphere). Even for the one-spacecraft option, we can increase the inclination to cover the polar region. *** I first could not really absorb this question but later (after NUVO question) that the panel considered precipitating ions at lows-altitude. Without remote sensing spacecraft, this question makes more sense. (4b) The estimate of return flux to be negligible is only an assumption. => Our answer: We have been working long on the inner magnetospheric ions, and the ion behaviors agrees with numerical simulations which predict the majority of the return flow has escaped. *** I wanted to tell that the NITRO covers region of all possible return flows pass by, and the orbit is carefully selected such that all return flows passes by. *** I should have also admitted that it is a kind of "assumption" but is well supported by observations. Such assumption are inevetable for any mission. (5) The best knowledge of proton escape rate is 3x10^26, and it is very hard to imagine that oxygen or nitrogen escape rate exceed it. => Our answer: 3x10^26 is a good estimate, but the escape rate changes time to time and cycle to cycle. Even Mars escape changes by an order of magnitude. *** I should have also shown the Akebono observation that shows higher escape rate for cold O+ than for cold H+, and I should have a slide of Cluster data of the case when O+ was higher than H+ in the magnetosphere. (6) What is the NUVO sensitivity of observing exosphere. => Our answer: 1 count / 1 R *** We thought this question (ESA's question form) is for remote-sensing SC's apogee, but it turned out to be for one-spacecraft option. Certainly the sensitivity of NUVO at apogee of in-situ SC is rather low, and also spin rate determines the angular resolution. So, we should have prepared additional slide of NUVO's scanning of exosphere from in-situ spacecraft (one-spacecraft, and its sensitivity. (7) Non-thermal escape is not mass-independent. => Our answer: Yes it is. *** We should have written "mass independent within isotope" instead of "mass-indpendent" in page 16 because the audience interpreted it N-O mass difference rather than isotope mass difference. (8a) Why Nitrogen escape catches up the oxygen escape? It is difficult to imagine how the stronger binding nitrogen catch up oxygen for large activity. => Our answer: It is because of different chemical reaction. Nitrogen is first ionized as N2+ and then dissociated. Oxygen is first dissociated and the ionized. *** I should have also mentioned that the element difficult to be ionized for small energy will be ionized when a sufficient energy is available. (8b) Related to the above, are there any exospheric models to visualize such reaction? If so, it should have been included in the proposal. => Our answer: Yes the models exist / Thank you, we should have included it. (9) You did not described the one-spacecraft option very much in term of science. => Our answer: The altitude resolution by NUVO, if it is placed on the in-situ spacecraft (one spacecraft option), is not as good as 100 km. Also, we need more assumptions in obtaining the exospheric profiles from NUVO, in estimating the (acceleration which is relevant to) the return flux without low-altitude ion measurements. Otherwise the science is the same. *** We should have prepared fore the science charge for both options, particularly giving correct altitude resolution with NUVO (5 km/s x 24 sec/spin = 120 km/spin). *** We should have mentioned the possibility of having neutral measurement mode for NIMS because in-situ spacecraft traverses exosphere (since spacecraft is fast moving there with about 130 km altitude range/spin, the resolution is much worse than two-spacecraft option, but yet it gives good first measurement). (10) There was public reach question: Suppose a EU research and education minister asks you why you want to spend 450 Meuros of taxpayers' money just to study Nitrogen around the Earth, what would be your argument on the importance of this mission? => Our answer: Nitrogen constitutes nearly 80% of atmosphere but we know too little about it compared to oxygen. Human being cannot leave questions of where our atmosphere comes from, and how it was associated with the life. ------------------------------------