MICA is a ground-based solar telescope placed in El Leoncito, Argentina, as part of a bilateral science program between Argentina and Germany. MICA is an advanced mirror coronagraph that complements the existing and planned solar telescopes in El Leoncito, especially HASTA. MICA is particular useful in producing reference measurements in conjunction with the SOHO mission. Close collaboration with international organizations running both ground-based and satellite-born instrumentation is intended.
1.1 Coronal physics
In this context MICA will produce an important contribution. The planned instrumentation allows an extremely sensitive and accurate determination of the sky transparency and the scattered light levels. Amount and spectral distribution of the sunlight scattered in the sky above the observatory are sensitive indicators of amount and type of atmospheric pollution. Therefore, MICA will measure the sky brightness in the visible and near infrared range of the solar spectrum. These data will be generated on a routine basis, every day in all four seasons, for several years. Similar measurements are being planned from observatories in the northern hemisphere. Close collaboration with atmospheric scientists of the various disciplines is intended in order to achieve a global understanding.
2.5. Measurements actually planned for MICA
l. The well-known green coronal line (the emission line of Fe XIV at ~2x106K) is addressed with a 0.9 nm wide interference filter at a wavelength of 530.3 nm. Due to the fully digitized imaging system immediate subtraction of reference images taken with a similar filter in the nearby continuum (e.g., at 526 nm) will reveal structures of the hot corona.
2. Similarly, the coronal red line (from the emission at 637.4 nm of Fe X at ~1x106K) will show structures of the cooler parts of the corona.
3. An narrow-band H-alpha filter (at 656.3 nm) will show the shape and evolution of cold prominences within the MICA field of view, an ideal complement to the HASTA observations of the sun disk in the same spectral range.
MICA profits from an enormous advantage ground observatories usually have compared to space instruments: an almost infinite transmission rate of observational data, the only limitations for MICA being the exposure time, the CCD camera read-out time, and the time it takes the computer to transfer data to the storage medium. We use a 90 MHz PC computer, two 9.0 GB fast hard disks and a sigh speed DAT device. We can look at images on the screen every 2 sec (for exposure times less than 0.5 sec, e.g., in H-alpha). Writing the image data on hard disk takes another 2 sec. A second computer (300 MHz PC computer) process the raw images in almost real time.
That illustrates one of the big advances MICA may achieve: High time resolution observations of fast bright transient phenomena in the lower solar atmosphere. It complements well the HASTA objectives. On the other hand, MICA ideally complements the measurements done by the LASCO telescopes from space.
3. Management section
3.1. General remarks
The SOHO LASCO space project required several models of the instruments to be built for undergoing the various test programs. That is the reason why we are presently left with at least one complete set of useful mirrors, other optical and mechanical components, electronic subsystems, even a complete telescope box. All that most valuable hardware is to be used in MICA. Especially, the most expensive optical components will be available. Others can be accommodated to the needs of MICA at low cost. The optical system has been developed and tested extremely carefully, such that there remains no risk for MICA. Also, there is a lot of technical experience in assembling, handling, testing and running the telescope, as a byproduct from both LASCO and the Bergmodell campaigns. Certainly MICA will benefit from the achieved quality standards set by a major international space project and from the experience the LASCO team has gained over the years.
Depending on the final MICA
time schedule parts of the work can be performed in
our MPS workshops, if the overall workload permits.
Part of MPS :
1. fabrication, assembly, test and
calibrations of MICA
telescope plus thermal canister and driver electronics,
2. installation of control computer plus operation software,
3. purchase of telescope mount and pointing system,
4. purchase of cupola and cupola interface
5. transport of equipment to Argentina,
6. installation and tests of telescope in El Leoncito,
7. participation in measurement campaigns,
8. data management, routine processing and distribution
9. data processing and scientific evaluation
1. assistance in telescope integration
by guest scientist,
2. organizing local infrastructure in El Leoncito,
3. modifications of observatory building,
4. transport of equipment in Argentina,
5. installation of cupola and telescope mount in observatory,
6. technical assistance in telescope installation,
7. running routine observation programs,
8. shipping data files to other participants,
9. data processing and scientific evaluation.
Scientists from both countries participate
in all phases of the project, including data evaluation and publications.
Mutual exchange of guest scientists is highly desirable.