Subaru Telescope Future Instrumentation

Internal Meeting for Instrument Planning toward 2020s


Attendees: Subaru staff members in Hilo, Instrument Planning Task Force members (Kashikawa, Masaomi Tanaka, Narita), and Mizumoto (from Mitaka)

Memo by Minowa-san

Iwata explained the reason why instrument planning is necessary now and a draft plan 
to be presented to Subaru Advisory Committee (SAC) and at Subaru Users Meeting in 

= Human resources and budget = 
* Assumption that NAOJ will try to keep the size of the Subaru operation at the same 
level as it is now until TMT is too optimistic (Arimoto) 

= PFS budget =
* Where does the PFS budget come from? (Jovanovic)
- IPMU has been raising funds for the development. NAOJ allocated additional budget 
for PFS starting from this year other than the Subaru operation cost. NAOJ managed to 
put some budget for PFS development (in addition to the telescope / enclosure 
modification required for PFS) this year, but is not guaranteed for next year. (Iwata)

= NsOpt =
*HDS presentation by Tajitsu-san
** HDS is the most reliable/stable instrument in the Subaru
**The throughput of HDS at UV range (300-360nm) is the best among 8-10m class 
telescope in the world. 
** Blue IMR at NsOpt needs to be relocated to keep the performance at UV. It costs 
about 1.5M yen. 

* Why is HDS better than VLT/UVES in shorter wavelength? (Imanishi) 
- UVES is using prism for derogating the image, while HDS is using K-type mirrors, 
which provides better throughput at extreme UV (Tajitsu). 

= Cs =
* SWIMS/MIMIZUKU (new PI type instruments from IoA, UT) can be alternatives of 
MOIRCS/COMICS, but it depends on the reliability of SWIMS/MIMIZUKU. 

* Acceptance of SWIMIS/MIMIZUKU should be affected for the decision (or hibernation) 
of the decommission of the Cs instruments 

* What is the science case of SWIMS/MIMIZUKU at Subaru? Are they achievable during 
the short stay at the Subaru? (Arimoto)

* To use SWIMS/MIMIZUKU as alternatives of MOIRCS/COMICS, they need to be 
evaluated their importance by using radar charts as we did for the other facility 
instruments. (Minowa)

* Do we need to continue the operation of MOIRCS/COMICS while commissioning 
SWIMS/MIMIZUKU? The performance of these instruments should be verified (Imanishi) 
- There is no extra standby flange to keep both instruments (Takato). 
- We might need to bring MOIRCS or COMICS down to ESB while commissioning 
SWIMS/MIMIZUKU. That means we would have to judge SWIMS/MIMIZUKU 
performance without on-sky tests (Iwata).

* If we decommission FOCAS, we will no longer use CsOpt. For S15A, among more 
than 20 times top-unit exchanges, CsOpt related ones are several. Does such reduction 
of TUE help day crew to reduce their workload? (Imanishi)
- It will not help a lot (Hasegawa)

* FOCAS presentation by Hattori-san 
** In early years FOCAS has been used mainly for MOS observations of high-z galaxies, 
but now the usage of FOCAS is changing to more versatile science cases using all 
modes (imaging, long slit, MOS, polarimetry). It is also used to try some new 
observation modes (e.g., fast readout).
** Image Slicer IFU is expected to be implemented in 2015.

* What is the uniqueness of FOCAS compared with the similar instruments at Maunakea? 
** FOCAS vs. Gemini/GMOS
- FOCAS sensitivity is higher than GMOS (Imanishi)
- Some science that do not require sensitivity (such as exoplanet) may be done with 
GMOS (Iwata)
** FOCAS vs. LRIS/Keck I 
- Keck-I demand is oversubscribed because of MOSFIRE 
- Keck TAC requested us to use KeckII for Subaru-Keck time exchange 
- Since LRIS is attached to Keck-I, it might be difficult to absorb all request to FOCAS by 
LRIS (Imanishi)
** FOCAS vs. KCWI/KeckII?
- Science case of the KCWI is narrow. 
- Although KCWI's capability is higher than FOCAS IFU, FOCAS is a more versatile 
instrument (Iwata)

= General Discussions = 

* Evaluation of the operation cost for each instrument might be helpful to decide 
which instrument should be decommissioned first (Jovanovic)

* Is there any technical risk to hibernate the instrument ? (Jovanovic)
- If serious failure happens with the hibernated instrument, we will not try to fix the 
failure, but decommission the instrument (passive decommission). (Iwata)

* Workload analysis 
- we might be able to consider the medium size development to reduce the workload 
for regular, but high load maintenance (e.g., Auto precooling system) or to prevent 
damage of the critical component (e.g., air flow to decelerate damage on blue IMR for 
HDS).  (Walawender)

* FMOS decommission 
** FMOS decommission is postponed to the end of S15B or later depending on the 
progress of PFS project (Iwata)
** If we keep using FMOS, we cannot avoid PIR<-->POpt2 top unit exchange, which 
should increase the risk of the failure (Imanishi)
** It might be better to consider the decommission of FMOS at the end of S15B 
regardless of the progress of PFS to reduce the risk of the failure (Imanishi). 
** It is important for the science strategy of the observatory to keep FMOS as long as 
possible and minimize the gap between FMOS and PFS. (Arimoto) 

* Upgrade plans for the existing facility instruments 
** There are several upgrade plans for the instruments that are subjected to the 
discussion of the decommission. Is there any possibility to increase the competitiveness 
by these upgrade? (Walawender) 
** FOCAS -- IFU, readout mode
** COMICS -- polarization mode
** MOIRCS -- new detectors, IFU
** HDS -- multi object unit 

* Possibility of the instrument exchange between the Subaru and the other observatory 
** Is it possible to transfer the instrument to the other observatory at Maunakea? 
- There was a discussion to transfer HDS to Gemini, but it is suspended. Using fibre 
reduces shorter wavelength throughput (Iwata)
- Interface between the telescope and instrument might be an issue (Walalwender) 
** Is there any possibility to transfer the instrument to TAO? (Guyon) 
- It is not likely as TAO is trying to minimize the operation cost by limiting the 
instrument capability to ones that have merit at high altitude environment. 

* Subaru's strategy at 2020s 
** Subaru's strategy at 2020s is to concentrate on wide field survey with HSC, PFS, 
and ULTIMATE and extrasolar planet study with PI type instruments. (Arimoto)

* General purpose instrument in future 
** There is no future plan for general purpose instrument to perform a wide variety 
of astronomical research. (Walawender) 
** If we decommission the existing instruments, Subaru will loose general purpose 
instruments. Does Subaru's community agree with this? (Walawender)
** There is no strong objection at previous UM against the Subaru's strategy at 2020s. 
Director will ask community again at the next Subaru UM (Arimoto). 

* Global strategy of 8-10m class telescopes 
** Is there any global strategy for the future of 8-10 m class telescopes (especially at 
Maunakea)? (Jovanovic)
- Subaru is regarded as survey type telescope using HSC, PFS, (and ULTIMATE). The 
other observatory will avoid those capability for their future plan (Arimoto). 
** Mauna Kea observatories basically agree the idea that we should avoid duplication 
of capabilities and share costs of instrument development through time exchange 
programs (Iwata).

* If we decide to continue operation of some of existing facility instruments, does 
that decision affect the progress of ULTIMATE-SUBARU? (Guyon)
- There might be some impact, but it should not be a primary reason of delay; 
development of ULTIMATE relies on contribution from outside (Japanese and foreign 
institutes). (Iwata)
-  Since ULTIMATE-Subaru is just a plan and has not funded yet, we also need to 
consider about the future without ULTIMATE-Subaru (new wide-field IR instrument). 
We might be able to reuse the existing instruments with the aid of the deformable 
secondary correction. It is better to postpone the decision of the instrument 
decommission until we have more solid plan of the ULTIMATE-Subaru. (Minowa) 
- Hibernation of the instrument is one of the solutions to such uncertainties in 
development of new facility instruments (Iwata)

* Iwata asked if there's any objection to the draft plan to be presented in SAC and 
Subaru UM. No strong objection was expressed. Iwata mentioned that we need to 
continue discussions based on feedbacks from community and with updated plan of PFS.
* Decommission of Cs instruments depends on acceptance or decline of 
SWIMS/MIMIZUKU carry-in proposals. We need to make decisions as soon as 
possible (iwata).

* Next discussion 
- It would be better to have another internal discussion meeting after UM with some 
opinions from the Subaru community (Arimoto)