S O L I S

Jack Harvey

The SOLIS project is progressing toward its initial operational capability target, now less than one year away. A number of critical milestones have been crossed in recent months:

• The mounting was moved without incident from the fabrication plant to its temporary home at the GONG prototype site about 5 km from the Tucson headquarters. Prior to the move, the mount drive motors were installed and tested with good results using dummy instruments.

• Work on the highest priority instrument, the vector spectromagnetograph (VSM), continued.

• Many of the optics mounts and mechanisms have been fabricated. For example, the main mirror cell is being used by a local optics company, which is now completing the telescope optics.

• The thermal performance of the spectrograph entrance slit and guider assembly, which receives the full solar flux from the 50-cm telescope, was tested at the McMath-Pierce telescope at the expected heat load. It performed in a comfortably cool manner and even survived a test in which the cooling system was intentionally shut off.

• Delivery delays in the VSM custom CCD camera and its data acquisition system are now significant problems. The latter problem has been addressed by selecting a powerful commercial data acquisition board in place of pursuing in-house development of the system. Development of data processing algorithms that support multiple processors and the data handling system data flow design continue.

• Observations with the integrated sunlight spectrometer (ISS) were made. As a result of this testing, a decision to change from a 600-µm diameter fiber optic feed to a 1000-µm fiber was made. Spectra from the K line to the He I 1083 nm line show good spectral resolution and low instrumental scatter in double-pass mode.

• The readout parameters of the ISS CCD camera were optimized. At a readout speed of 300,000 pixels per second, the readout noise is 22 electrons per pixel and the full-well capacity exceeds 200,000 electrons with excellent linearity. Development of flat fielding techniques is now underway.

• All of the off-the-shelf optics for the full disk patrol (FDP) instrument have been received.

• The software systems for controlling all of the SOLIS hardware and for acquiring data continue to show good progress. A GUI front end to the ISS system has been installed and tested. Revisions to the NSO digital archive are underway in preparation for SOLIS data.

• Recruitment of a data scientist for development of FDP and ISS related reduction algorithms was initiated.

Caption: SOLIS mount installed at GONG farm temporary site. Left to right: David Woolever (Vroom Engineer & Manufacturing, Inc.), Mark Warner (SOLIS), James Robinson (SOLIS), and David Vroom (Vroom).