# Presentation: 932400

## Solar-B12 Weeks to Launch and counting June 30, 2006John M. DavisSolar-B Project Scientist 

## Solar-B is an international collaboration between the Space Agencies of Japan, the USA, the UK and Europe.
It contains three instruments to provide coordinated observations that will follow the generation, transport and ultimate dissipation of magnetic energy from the photosphere to the corona. The instruments are:
a high resolution optical telescope that provides spectrally resolved images, Dopplergrams and vector magnetograms
A high resolution X-ray telescope that provides coronal temperature and density maps
An EUV imaging spectrometer that provides spatially resolved high resolution spectra.
Solar-B’s advantage over previous missions lies in its ability to measure vector magnetic fields. 
This provides quantitative knowledge on when, where and how the field is twisted or sheared and how this stored energy is released to heat the corona and power eruptive events. 

- It contains three instruments to provide coordinated observations that will follow the generation, transport and ultimate dissipation of magnetic energy from the photosphere to the corona. The instruments are:
- a high resolution optical telescope that provides spectrally resolved images, Dopplergrams and vector magnetograms
- A high resolution X-ray telescope that provides coronal temperature and density maps
- An EUV imaging spectrometer that provides spatially resolved high resolution spectra.
- Solar-B’s advantage over previous missions lies in its ability to measure vector magnetic fields.
- This provides quantitative knowledge on when, where and how the field is twisted or sheared and how this stored energy is released to heat the corona and power eruptive events.

- Mission Overview

## The Solar-B Spacecraft

- The Solar-B spacecraft is built around  the optical telescope assembly (OTA).
- The focal plane package (FPP) of the OTA, the XRT  and EIS  are strapped to the sides of the OTA.
- The payload has a dry weight of  875 kg, the solar arrays provide 1000 w of power and the telemetry systems has a downlink capability of 4.2 Mbps.
- ESA is providing 15 contacts per day from Svalbard to supplement the four daily passes at Kagoshima for a total of ~ 7 Gbytes per day.

**Two Views of Solar-B**

##                   The Solar Optical Telescope (NAOJ)

-                   The Solar Optical Telescope (NAOJ)

** ****Telescope**
-  F9, aplanatic,Gregorian with a 50 cm aperture.
- Diffraction limited performance 388-670 nm
- Angular resolution is 0.2’’ at 400 nm
- The field stop restricts the FOV to 4x4 arcmin2
- The structure is a zero CTE CFRP
**Mirror**
- Fabricated by REOSC from ULE and has a protective Ag coating
- 18.2 nm wavefront error
**Total System (****OTA,FPP,CT****)** wavefront error
-       < 47.5 nm
- 	   The **OTA **also** **contains the **polarization                  ****	****modulator** for the magnetographs and the 	   	**tip/tilt mirror** for the Correlation Tracker

**The OTA is the largest optical telescope to observe the Sun from ****	****	****	****space**

## The Completed OTA Assembly

## Optical Testing

## The Focal Plane Package (LM/HAO)

- The **Spectropolarimeter **(HAO) records full Stokes profiles of the magnetic field
- Slit Width    	     1.6 x 164 arcsec2
- Spectral Range	      6302±.05Å
- Spectral Resolution	25 mÅ
- Polarimetric Accuracy 	104
- The **Broad Band Filter** **Imager** retains the highest  spatial resolution **(****0.053 arcsec pixels) **for photo and chromospheric imaging in six bands between **380 – 670 nm**
- The **Narrow Band Filter** Imager measures vector magnetic fields and Dopplergrams using a tunable filter
- Spectral Coverage 5170 – 6570 Å
- Magnetic Sensitivity 5 G (long); 50 G (trans)
- Doppler Velocities 50 – 100 ms-1

- The **FPP** contains three instruments:
- a spectropolarimeter,  a broad band imager and a narrow band imager
- Dimensions: 1.63 x 0.65 x 0.37 m3
- Mass:            48.4 kg

## Correlation Tracker  and Image Stabilization

-  The telescope is  pointed using a sun sensor and the spacecraft provided attitude control system The pointing stability ranges from:
**0.7 arcsec/sec to 5 arcsec per hour.**
-  To recover the diffraction limited performance of the OTA, a correlation tracker (CT) controls a tip tilt mirror (CTM) located in the collimated beam exiting the OTA. The CTM was developed by ISAS and the CT by LMATC.
- The combination  improves the expected image stability  for the OTA/FPP to:
**0.06 arcsec/10 sec and**** 2 ****arcsec per hour.**

## The EUV Imaging Spectrometer (MSSL/NRL)

- The EIS is a joint effort  between **MSSL** (structure, cameras, control electronics and software) and **NRL** (optics and filters).
- EIS provides **temperature and density diagnostics** of coronal and transition region plasmas and will attempt to **detect reconnection flows. **
- An off-axis paraboloid mirror illuminates various slits placed at the focus of a toroidal grating that disperses the spectrum onto two detectors.
- Properties
- Wavelengths 170-210 Å, 250-290 Å
- Resolution: Spatial 1.0 arcsec pixel 			Spectral 2.23 mÅ per pixel
- Slits1 x 512 and 2 x 512 arcsec2
- Slot 40 x 512 and 250 x 512 arcsec2

**Final Preparations for EIS**

- Are you sure you heard something drop?

## 	The X-Ray Telescope	(SAO/ISAS)

- The XRT is a collaborative effort between SAO (mirror, filters, structure and mechanical systems) and ISAS (camera sensor and electronics).** **
**The telescope **is a modified Wolter I with a 0.3 m aperture and a 2.71 m focal length. It has on-orbit** focus adjustment** and provides a **flare flag** to alert the other instruments.
- Properties
- Angular Resolution 2 arcsec
- Encircled Energy: 68 % within a 2 arcsec diameter circle at 0.523 KeV
- Improved temperature sensitivity over the range from 1–30 MK gained from using a back thinned CCDwith improved low energy response

**Mounting the XRT to the Spacecraft**

- Length 3.0 m, Diameter 0.42 m (max)
- Mass 48.4 kg

## Fields of View

**EIS has a coarse drive to independently offset **
**  ****on the NS axis from the OTA pointing axis**

## Automatic Tracking

- ω is commandable from the ground in the range of 0.15 – 0.26 rad/day.

- Limb viewing

- Change to new target

- SOT FOV

- θ(*t*) = θ(*t0*)
- φ(*t*) = φ(*t0*) + ω*t,*

- SOT FOV

- SOT FOV

- SOT FOV

- SOT FOV

- SOT FOV

- Polar Observation

**Solar-B can select and track any region on the Sun**

## The Data System

-  The science instruments are controlled by the ISAS developed Mission Data Processor (MDP)
-  The MDP uploads commands and oversees the interaction between the Data Handling Unit (DHU) and the individual science instrument controllers. The DHU compresses and stores data for transmission
-  Normal memory allocation is 70% for FPP and 15% each for EIS and XRT and is changeable from the ground. The DHU prevents instruments from exceeding their data allocation.

## The Observations

- Detailed planning for each days observations starts approximately 36 hours before the observations sequences are uplinked.
- Observations sequences are sent to the spacecraft during the evening passes (1100 UT) in Japan and cover a 24 hour interval.
- In extreme cases it is possible to make minor adjustments to the target position or sequences as little as 8 hours before the observations sequences are sent to the spacecraft.
- After the first six months all observations will be made available to the scientific community as soon as they are processed at ISAS.
- An open data policy
- Proposals for observations after the first six months should be submitted to the Scientific Schedule Coordinator (SSC). Each instrument team has two SSCs whose are there to help you.

## Current Status and Schedule

- The spacecraft is undergoing its final system performance test before shipping to the Uchinoura Space Center on July 30, 2006
- The first planning & operations simulation is scheduled for July 5-6.
- The final optical performance tests are scheduled for July 7-11.
- The earliest launch date is 2130 UT on 22 September with a launch window that ends on 30 September.
- If Solar-B is not launched during this window the next opportunity is in the late November early December time frame.
- Spacecraft verification and checkout is scheduled for October.
- First light for the three instruments will occur in November.
- December is set aside for performance verification and in-flight calibration.
- The initial observing phase will begin in January 2007.

##  	Visit the Solar-B website	http:// solarb.msfc.nasa.gov

- Concluding Remark