The DR (Design Review) meeting for FOXSI happened today at the Wallops Flight Facility. Everything went smoothly though a few action items were noted. Some bullet points from my notes follow (revised 10/19/2009 to include suggestions by L. Glesener):
- During the launch (i.e. with the motors firing), we can expect short (millisecond) drop-outs in power. We should consider (and test) how these power drop-outs will affect us.
- It was noted that a previous experiment had a problem with saturation which paralyzed their experiment. We should add such a test to our procedures.
- The exact location of the cooling system which will hang on the rail, preferably as close to the payload as possible, has not yet been resolved. Ted Nelson(?) may be able to help out with this problem or someone could travel to White Sands prior to launch to figure this out on site
- For range safety, a complete procedure needs to be written up about the FOXSI alignment process (using the x-ray tube) and sent to Wallops. All lasers (even those whose power output is less than 5 milliwatts) need to be declared through some forms provided by Wallops. Also, all radioactive sources need also be declared. Forms can be gotten from T. Gass.
- A stand (which can be leveled) to hold the the FOXSI payload can be provided by Wallops. It would be useful to get some photos of it.
- Connectors and cabling for the shutter door and SPARCS will be delivered to SSL for harnessing.
- The shutter door may also be delivered to SSL.
- The SPARCS system has never been pre-programmed for multiple targets in the past. Command uplink is the usual method which means that we will always have a choice to go to the next target or not. The exact sequence need to be discussed in light of the minimum mission success criteria.
- A accelerometer will be provided by Wallops during the vib test and can be placed anywhere. Paul suggested it be placed on the free end of the metering tube.
- It was noted that the range requires clearance to allow the rocket to transmit. Since clearance is not always possible, a direct wired connection to the formatter output would be useful.
- SPARCS takes about 4 seconds to move from one target to another. Also, SPARCS need to be within 20 arcminutes (1200 arcseconds) of Sun center to be able to do its job. The pointing alignment is most sensitive to the LISS alignment to instrument.
- There are currently 8 other experiment flights ahead of FOXSI.
- As of today a rocket has been committed for the FOXSI flight but manufacturing is behind therefore there is no actual rocket available.
- There is some contention at Wallops about not having solar missions meet first at Wallops to ensure that the mission is ready before sending everyone to White Sands. Until further notice, the plan is still to go straight to White Sands for mission readiness review.
- Need a new uplink command to enable the shutters (one time event).
- White Sands will not schedule the launch date until I&T is finished. If I&T occurs/completes on schedule, then we can expect the launch plan to be within a week or two of the currently estimated date.
Some more notes (added 10/19/2009)
by Steven Christe, Sam Krucker, R. P. Lin
Space Sciences Laboratory, University of California, Berkeley, CA 94720
The Astrophysical Journal, Volume 680, Issue 2, pages 149-152 (ADS link)
Abstract
During a period of 12 minutes on 2002 July 19 14:23-14:35 UT, the WAVES instrument on WIND observed six interplanetary type III radio bursts, one approximately every 2 minutes, and each was accompanied by a weak hard X-ray (HXR) burst (12-15 keV) observed by RHESSI. The radio bursts are observed up to 150 MHz with some up to 600 MHz. Simultaneous observations by TRACE show jetlike eruptions emanating from the region of HXR emission. The observed HXRs are inconsistent with emission from the escaping type III-producing nonthermal electrons. We suggest that the type III acceleration process may be associated with an explosive release of <~5×1026 ergs in the form of a “superhot” (26 MK) thermal plasma in the corona, an energy comparable to that associated with the type III-producing electrons.
by Pascal Saint-Hilaire, Sam Krucker, Steven Christe, and Robert P. Lin
Space Sciences Laboratory, University of California, Berkeley, CA 94720
Received 2008 August 21; accepted 2009 February 2; published 2009 April 20
The Astrophysical Journal, Volume 696, Pages 941–952, 2009 (ADS link)
Abstract
We study the detectability and characterization of electron beams as they leave their acceleration site in the low
corona toward interplanetary space through their nonthermal X-ray bremsstrahlung emission. We demonstrate that
the largest interplanetary electron beams (1035 electrons above 10 keV) can be detected in X-rays with current and future instrumentation, such as RHESSI or the X-Ray Telescope (XRT) onboard Hinode. We make a list of optimal observing conditions and beam characteristics. Amongst others, good imaging (as opposed to mere localization or detection in spatially integrated data) is required for proper characterization, putting the requirement on the number of escaping electrons (above 10 keV) to 3
× 1036 for RHESSI, 3 × 1035 for Hinode/XRT, and 1033
electrons for the FOXSI sounding rocket scheduled to fly in 2011. Moreover, we have found that simple modeling
hints at the possibility that coronal soft X-ray jets could be the result of local heating by propagating electron
beams.
Steven Christe [1], S. Krucker [1], L. Glesener [1], B. Ramsey [2], T. Takahashi [3]
1 Space Sciences Lab, U.C. Berkeley
2 NASA/M.S.F.C., Huntsville
3 Astro-H team, Japan
Presented at SPIE 2009 (link)
Abstract
The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA sounding rocket payload scheduled to fly in late 2010 to observe hard X-ray emission (HXR) from the quiet Sun. To date, the most sensitive HXR images are made using a rotating modulating collimator aboard the Reuven Ramaty High Energy Spectroscopic Imager satellite (RHESSI). However, the rotating modulation technique is intrinsically limited in sensitivity and dynamic range. FOXSI uses nested-shell, grazing-angle optics and silicon strip detectors to achieve an angular resolution of 12 arcsecs (FWHM) and ~1 keV energy resolution. FOXSI will be a pathfinder for future solar HXR observatories.
The FOXSI SPIE proceedings manuscript has just been submitted! Now FOXSI is finally part of the official record and not just a proposal!
We are finally back from the Stray light facility at the MSFC after completely some tests though not the ones we were expecting. After testing the single-shelled FOXSI module, it was clear that something was wrong. The laser alignment seemed to suggest that something was off with the shell. We were unable to get the laser down to a nice clean spot. The subsequent x-ray tests confirmed this. The focus was not a spot but always a ring. We tried to focus by searching in the z direction but hit up against the end of the z stage. The z stage was centered when we closed the bell jar so alignment was probably not the problem. Also, the image was not a perfect ring but had a large asymmetry which was suggested to be caused by a problem with one of the spider grooves. Since the spider had not been cleaned, it is possible that a small piece of metal was stuck in the grove with the shell pushing it out of true. This theory does not explain why we were not able to focus down to a point.
After this poor showing by the FOXSI module, we put in a single FOXSI shell. This shell was mounted at the center in a a plate with a circular cutout. The shell was dropped into the hole and four spots of epoxy hold it in place (the usual method is to have the shell float in the circular opening and apply epoxy all around the opening). This shell gave much better results. Analyzed images coming soon…
After some delays, we finally have a single-shelled foxsi module and are setting up for some testing at the Stray Light Facility at the Marshall Space Flight Facility. Unfortunately the scheduled vibration test has been canceled for this week.
The foxsi module in the bell housing waiting for an optical laser alignment.
Steven Christe [1], S. White [2], S. Krucker [1]
1 Space Sciences Lab, U.C. Berkeley
2 Astronomy Department, University of Maryland.
Presented at AAS/SPD 2009 (link)
Abstract
We present a statistical survey of RHESSI microflares observed in hard X-rays (HXR) with simultaneous observations by the Nobeyama Radio Heliograph at 17 GHz and 34 GHz. These microflares were found using a new flare-finding algorithm designed to search the 6-12 keV count-rate when RHESSI’s full sensitivity was available, in order to find the smallest events. Between March 2002 and March 2007, a total of ~25000 events are identified, of which ~8500 are also observed by Nobeyama at 17 and 34 GHz. We compare HXR and radio fluxes and analyze the relationship statistically. When the events are detected at both wavelengths, the relationship between the lightcurves falls into several classes. Radio and HXR images of a small selection of events are used to investigate the relative locations of the two emissions, and we discuss the physical conditions that affect the relationship between the HXR and radio emission.
Steven Christe [1], L. Glesener [1], S. Krucker [1], B. Ramsey [2], T. Takahashi [3], R. Lin [1]
1 Space Sciences Lab, U.C. Berkeley
2 Marshall Space Flight Center
3 ISAS/JAXA
Presented at AAS/SPD 2009 (link)
Abstract
The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA Low Cost Access to Space sounding rocket payload scheduled for launch late 2010. FOXSI will provide imaging spectroscopy with high sensitivity (~50 times RHESSI) and high dynamic range (~100) in hard X-rays (HXR) up to 15 keV. For the first time, it will be possible to search for nonthermal emission of thermal network flares occurring in the quiet corona in order to determine whether they are similar to active region flares. Additionally, FOXSI will extend the active-region flare distribution to events two orders of magnitude smaller than previously observed and determine their contribution to coronal heating. FOXSI is able to achieve this unprecendeted advance in solar HXR observations through the combination of nested HXR optics developped by the Marshall Space Flight Center and novel silicon strip detectors provided by ISAS Japan. The FOXSI mission will provide HXR spectroscopic imaging with an angular resolution of 12″ (FWHM) and ~1 keV energy resolution. FOXSI will be a pathfinder for the future generation of solar HXR spectroscopic imagers.
Steven Christe [1], K. Watanabe [2], S. Krucker [1]
1 Space Sciences Lab, U.C. Berkeley,
2 ISAS/JAXA, Japan.
Presented at AAS/SPD 2009 (link)
Abstract:
In this study we investigate the relationship between RHESSI flares and white light emission as observed by Hinode/SOT at 3968.6 angstroms (Ca II H line), 4306.4 angstroms (G band), and 4505.1 angstroms(blue continuum) images. The emission mechanism for white light emission in flares is not yet understood though it is believed that emission at these wavelengths originates from the chromosphere, photosphere, and deep photosphere respectively. Using a combination of the official RHESSI flare list and a microflare-finding algorithm, we investigate all RHESSI flares with simultaneous observations by RHESSI and Hinode/SOT (a total of ~200 events). Single event studies suggest that microflares are frequently observed in Ca II H line. Photospheric emission is searched for using the location of the Ca II H line chromospheric emission. We discuss the physical conditions necessary that may affect the relationship between HXR and white light emission.
