Swift Mission Director's Status Report Log - December 2004
Dec. 31, 2004
Swift entered Pre-Planned Target mode on the first command pass of the day, so that the BAT could conduct a simultaneous observation of the Crab Nebula with the RXTE satellite. The XRT was pointed at the Crab, so it should also have simultaneous data.
On the next pass Automated Target (AT) slewing was enabled, so should a GRB be detected by a BAT trigger, (and if the GRB location is outside the Swift viewing constraints from the Sun, Earth and Moon), then Swift should autonomously slew to the new GRB. We will continue to manually inspect BAT GRB candidates to assure that they are reliable before posting them on the GCN.
We plan to keep Swift in AT slewing mode through at least Jan. 2. We look forward to resuming activation of the UVOT starting on Jan. 4.
Dec. 30, 2004
Swift completed its recovery from safehold and is back to its fully operational mode. We will be entering Automated Target slewing on Day 366, to enable Swift to point the XRT at new BAT discovered GRBs as rapidly as possible. We will still carefully monitor the BAT triggers to manually check their reliability.
The BAT team reported their results from observations of the superflare emitted by SGR1806-20 on Dec. 27 (GCN Circ. 2925). Unfortunately this object is located too close to the Sun to allow any XRT observations, even as Targets of Opportunity.
It's interesting to note that the BAT electronics were sized to handle a BBOY (Brightest Burst Of the Year), with the expectation that we might see one such event per year. BAT has already (including the SGR event) now seen three events of BBOY level within about a week of BAT trigger activation.
Dec. 29, 2004
Swift entered an ACS Safehold at 13:27:17 UT on Day 364. Investigation has shown the safehold resulted from a manuever initiated by the spacecraft between planned targets which was allowed by the Earth and Moon constraints, which became invalid before the time the spacecraft completed the manuever.
We are restoring Swift to normal operational mode, and will investigate operational and parameter changes which will protect us from repeating this situation.
Dec. 28, 2004
BAT detected another burst (reported in GCN Circ. 2918): At 10:49:13 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board GRB041228. The spacecraft did not autonomously slew to the burst since automated slewing was not yet enabled.
The BAT ground-calculated location is RA,Dec 336.641,+5.050 (J2000) with an uncertainty of 5 arcmin (radius, 3-sigma, including a systematic uncertainty). The lightcurve is multi-peaked with a main emission duration of ~40 s, with 36 counts/cm^2 fluence and a peak (1 second interval) of ~1.2 counts/cm^2/s in the 15-350 keV band. And there appears to be extended emission for another 80 sec.
XRT performed centroiding tests today. Good progress was made. Tomorrow XRT will be performing roll angle thermal tests.
Dec. 27, 2004
BAT detected another burst (reported in GCN Circ. 2914): At 20:34:19 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board GRB041226. The spacecraft did not autonomously slew to the burst since automated slewing was not yet enabled.
The BAT ground-calculated location is RA,Dec 79.544,73.349 with an uncertainty of 6 arcmin. The lightcurve is multi-peaked with a main emission duration of ~20 s, with 4 counts/cm^2 fluence in the 15-350 keV band.
XRT continued orientation testing of the thermal effects on the XRT radiator. Tomorrow XRT will conduct centroiding accuracy calibration to improve the accuracy of the XRT derived positions.
Dec. 26, 2004
Swift crossed another milestone with its first successful interval of lights-out operations. No event pages were recorded and the satellite successfully performed normally for eight hours without hands-on operation at the MOC. We will continue lights-out operations from midnight to 8 AM for the rest of this week.
The XRT continued to conduct thermal orientation testing. With the XRT pointed at the southern orbit normal position the XRT grew quite cold (orbital temperatures varying from -60 to -64 C); but at the opposite orbit normal (in the north) the temperatures rose. These data, combined with in-depth thermal modelling, should enable us to understand how to maintain XRT at operating temperatures below -50C.
BAT discovered no new bursts in the past 24 hours.
Dec. 25, 2004
Swift spent a good Christmas and Christmas Eve. On Dec. 24, BAT found another burst: At 20:20:57 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board GRB041224. The spacecraft did not autonomously slew to the burst since automated slewing was not yet enabled. (GCN Circ. 2908)
The BAT and XRT teams refined and improved analysis of the previous burst, GRB041223. The XRT narrowed the position measurement, posted a light curve and gave a spectrum (GCN Circ. 2910); BAT provided an improved spectrum and fluence (GCN Circ. 2909).
Christmas at midnight started the first 'lights-out' operation of Swift - where we close the MOC and check from home. Flight Operations Team members return to the MOC to conduct checks and routine uplinks on a schedule of once per eight hours. The Instrument teams are also conducting routine monitoring, while the Pre-Planned Science Timeline is executed on-board the satellite.
Dec. 24, 2004
Swift's XRT instrument successfully detected the X-ray afterglow to GRB041223. Reported in GCN Circ. 2901, the XRT was pointed at GRB041223 on 2004/12/23 at 18:43:59 UT for 1490 s, at 20:16:24.4s for 1600 s, and at 21:50:40 for 430 s. The spacecraft did not autonomously slew to the burst since automated slewing is not yet enabled and the XRT is in the midst of engineering measurements.
The XRT position was confirmed by optical and NIR ground based observations from Las Campanas and the VLT (Circ. 2901 & 2902). X-ray spectra and light curves were measured by the XRT team. This important milestone shows that Swift's BAT and XRT can operate smoothly together to carry out rapid identification of GRBs. Once operational testing is finished, we will enable automated spacecraft slewing, which will reduce the response time from 4.5 hours (on 041223) which resulted from a Target of Opportunity response, to typical response times of 1 minute (from an Automated Target response).
Dec. 23, 2004
The Swift BAT found its sixth GRB, reported on GCN - GRB041223 (GCN Circ. 2898). At 14:06:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board GRB041223. The spacecraft did not autonomously slew to the burst since automated slewing was not yet enabled. The BAT ground-calculated location is RA,Dec 100.183,-37.066 (J2000) with an uncertainty of 7 arcmin.
The burst lightcurve is multi-peaked with structure within the peaks with the main emission lasting ~60 sec. The peak flux was 7.5 events/cm^2/sec (~28 Crab). The total duration was ~130 sec.
Swift conducted thermal orientation testing to explore the sensitivity of the XRT radiator to a controlled set of variables. This testing is expected to last for the next week.
Dec. 21, 2004
The Swift BAT found its fifth GRB - GRB041220 (GCN Circ. 2890). Automated notification to the BAT Team through TDRSS was partially enabled for this burst. The burst is a fast-rise exponential-decay (FRED) with a full-width at half-max of ~2 sec. There is some indication of emission out to 18 sec after the peak. The peak flux was about 8 Crabs in the 15-350 keV band.
Swift conducted calibration observations of the Crab for both the BAT and XRT. Although the Crab is located at a poor heating orientation for the XRT radiator, the XRT group was able to obtain both a spectral fit to the Crab data, and to successfully extract phase resolved light curves of the pulsed X-ray emission at the temperature of -50C.
Dec. 20, 2004
The BAT outdid itself - detecting three separate GRBs on Dec. 19! These were reported in GCN circulars: GRB041219a (Circ. 2874), GRB041219b (Circ. 2883), and GRB041219c (Circ. 2886). GRB041219a is especially impressive, ranking in the top 1-2% in fluence and duration, and had an early precursor arriving about 5 minutes prior to the main burst. When Swift is activated, such a burst will enable the XRT and UVOT to be positioned on the new burst even before the main outburst.
Also important is that GRB041219a was simultaneously observed by Integral, providing both a potential for cross-calibration, and confirmation of the reliability of Swift as a GRB detector.
Dec. 19, 2004
The BAT triggered on GRB041219 (GCN Circ# 2866, D.Gotz et al.), at 01:42:18 UT. The spacecraft did not autonomously slew to the burst since automated slewing is not yet enabled. The burst lightcurve is multi-peaked with structure within the peaks. After an initial pair of small precursors, the peak intensity increased to 25 events/cm^2/sec, equivalent to 43 Crabs, with a total duration of 520 seconds.
Dec. 18, 2004
Swift conducted tests of the autonomous response process. The Figure of Merit (FoM) team commanded various trials of how Swift would respond to targets generated either internally (via a BAT trigger) or externally (via a ground uploaded position, called a Target of Opportunity [ToO]). In conducting these tests we chose actual targets of interest, including the GRB041217 (discovered by Swift yesterday), the transient pulsar V0332+53 (currently in outburst) and the GRB recently reported by the Integral team.
Dec. 17, 2004
Swift had a triply successful day! Swift reported to the GCN its first BAT discovered GRB! GRB041217 was detected on Dec 17 2004, 7:28:30 UT when the BAT triggered and located on-board an apparent gamma-ray burst. The spacecraft did not autonomously slew to the burst as automated slewing is not yet enabled. The location is RA/Dec 164.79, -17.95. The Swift attitude control system is still undergoing calibration, but we estimate that the position error is less than 12 arcmin.
The UVOT successfully turned on its Telescope Module electronics, and conducted several exposures (without moving the filter wheel, which has its blocked filter to the sky). All tests were successful.
The Swift spacecraft team presented the current spacecraft status at the Spacecraft Acceptance Review (SAR). The GSFC Project team agreed to accept the spacecraft from General Dynamics (originally SpectrumAstro). After L+30 days, responsibility for operating Swift will be assigned to the Penn State MOC.
Dec. 16, 2004
Swift's BAT has successfully detected its first X-ray pulsar! The transient pulsar, V0332+53, has been detected over the past ten days in the BAT data. Fourier analysis of these data has found a very strong and sharp feature at extremely high confidence level at the first harmonic of the pulsar frequency. This observation confirms that the timing properties of the BAT are good. We will load the appropriate pulsar parameters into the flight software registers to allow on-board extraction of data for this pulsar.
The XRT conducted efforts to extract information from the relay board controlling the XRT Thermo-Electric Cooler. Three of four tests were carried to conclusion, but we have not discovered any new information which might enable us to turn on the TEC.
Tomorrow the UVOT team will start the process of turning on the Telescope Module electronics.
Dec. 15, 2004
Swift is conducting boresight alignments between the XRT and the star tracker. Yesterday new alignment parameters were put into the star tracker, and today we collected data from several X-ray emitting stars to confirm (and possibly refine) the alignment settings.
BAT has collected data to refine its parameters as well. These will be uploaded and tested tomorrow. They will start to upload additional commands to increase the BAT sensitivity when a bright pulsar is in the field of view (expected to be the Crab on Saturday).
Dec. 14, 2004
Swift has succeeded in opening its final door! The UVOT team successfully commanded the opening of the UVOT door at 14:01:20 UT. The opening occurred exactly on plan, and we received nominal deployment and latching messages. The heaters and temperatures are behaving as expected with the additional heat loss effects predicted for the open door. We plan to allow the UVOT to out gas in the door open state until Friday, when we will activate the UVOT Telescope Module electronics.
BAT is collecting data to start with further adjustments to the detector thresholds and BAT trigger settings. The spacecraft is preparing to upload new coordinates for the star tracker offsets. Tomorrow we plan to take more star tracker to XRT boresight measurements.
Dec. 13, 2004
Swift activation moved into areas of joint operations between systems. Today the XRT and star tracker simultaneously observed X-ray emitting stars, and measured positions in both energy bands. We will analyze those data, and derive offset parameters for the star tracker to make the tracker coordinate system match with the X-ray telescope-detector coordinate system.
The BAT team reviewed its data and found that the recent gamma-ray burst, GRB 041211E, was detected by the BAT instrument. Because the burst was bright enough to trigger even the BAT's 100 sigma rate thresholds, 041211E was processed by the BAT's imaging system. 041211E was outside the BAT coded field of view, so no burst was reported. Nevertheless this is exciting confirmation that BAT will be a capable instrument for the discovery of new GRBs!
Dec. 12, 2004
Swift is busily digesting the extremely exciting activities of yesterday. The Swift XRT door opening yesterday has been followed by calibration observations of Cas A, Mrk 421, and NGC 2516. The XRT images show good imaging performance, and the spectra are also good.
BAT has now activated the entire detector array, and raised the high voltage to the planned operational state of 200 V. The operational array temperature is being adjusted, and they are deciding on whether to keep the array at the current temperature or raise it another 1.5 degrees. The detector thresholds are being carefully lowered to determine the proper operational settings. In parallel the BAT team is revising trigger settings to start closing in on GRB responses by Swift.
Tomorrow we plan to conduct boresight alignments, where we observe sources which are bright in both X-rays and optical light, with the aim of adjusting the star tracker parameters to make the target points of the trackers and the XRT identical. Tuesday we hope to open the UVOT door.
Dec. 11, 2004
A great day for Swift! We both opened the XRT inner door, and enabled the entire BAT array. The teams are very happy, and we look forward to the next week, when more of the focus turns toward opening the UVOT door, and starting its activation.
BAT completed its turn-on of the entire array (32,768 detectors). We have enabled the BAT trigger software in a de-sensitized state, and will conduct tuning operations for the detector parameters (including high voltage and thresholds) and for the many BAT trigger conditions (which creates the alerts which Swift uses to respond to new GRBs). Analysis of the data so far has detected seven different persistent point sources in the BAT, which are all consistent with known gamma-ray sources.
XRT door opening happened smoothly on the first try. The spacecraft orientation during the night was oriented to maximize the cooling properties of the radiator (by turning the XRT radiator away from the Earth), and the XRT collected data from the door source at a temperature 5-10 C colder than we've seen in normal operations. This will be helpful in understanding our calibration with respect to temperature, and is an operational assistance to compensate for lack of a TEC.
Tomorrow we will be collecting calibration data from sky sources for the XRT, and fine tuning BAT parameters.
Dec. 10, 2004
The BAT made more progress toward activation. It has now completed turning on the entire array, except for the high voltage on the last quadrant of detectors. We hope to complete the BAT detector turnon tomorrow.
The XRT continues to collect door-closed data, and has extracted flight data into spectra from all its operating modes, both from our quick look processing here at Penn State and through the pipeline processing system at the Swift Data Center at GSFC, to the Data Centers at Leicester and Brera.
We plan to open the X-ray camera door over the weekend, when we hope to see the first X-rays from the sky in the XRT!!
Dec. 9, 2004
Swift is making preparations for opening the XRT Focal Plane Camera Assembly door early on Saturday morning. Today we held discussions with the Spectrum ACS people to convince ourselves that the ACS is both stable and accurate enough to trust to control the satellite with XRT fully open to the sky. Tomorrow we will conduct a review of the XRT readiness for door opening, and plan to open the door on Saturday.
BAT started the turn-on process for activating the second Loop Heat Pipe. The final quarter of the BAT will be activated after the LHPs are turned on.
The ACS discussion has concluded that the spacecraft is well enough understood and performing well enough to allow the door to be opened on Saturday.
Dec. 8, 2004
Swift XRT had a very busy day today. The Figure of Merit testing has completed its first phase successfully. We lowered the BAT trigger thresholds until the normal noise levels caused a BAT trigger (i.e. as if a new GRB had occurred). The BAT, FoM and spacecraft all coordinated perfectly on the first try, and we received BAT trigger messages relayed to the GCN, and the spacecraft slewed to the new target exactly as planned. This test was so successful and so prompt that we were able to execute a second BAT trigger and slew within a single 10 minute commanding window.
The BAT turned on more detectors, so that 3/4 of the entire array is now powered up. Tomorrow the BAT plans to turn on the second set of Loop Heat Pipes, which are required for cooling when the entire array is operational.
We are now controlling the Swift pointings using the Pre-Planned Science Timeline, which is produced by the Swift MOC Science Planner, and then uploaded to the spacecraft as an ATS load. The ATS load typically covers at least one or two days of operations. Previously the ATS only instructed Swift on when and where to look to establish telemetry contacts. Now we use the ATS to instruct the Swift satellite to point at the locations specified in the PPST. This is our long term plan for controlling Swift, and so far it is working smoothly.
XRT continues to use command passes to gather calibration data from the CCD operating under the planned modes, but at the current temperature. The XRT team at Leicester has successfully used XRT and BAT data files generated from the Swift Data Center and run the normal analysis software tools on that data. In particular the XRT data (in Photon Counting mode and Grade 0 [single] events) were successfully fit using XSPEC and the pre-flight response matrices. This indicates that the XRT are fully usable even without the TEC, although substantial work remains in adjusting our operating parameters and our analysis files.
Dec. 7, 2004
Swift XRT had a very good day today. At about 4:40 AM, local time, the XRT outer telescope door opened exactly on schedule. The deployment was completely nominal, with both actuators firing as planned. The mirror temperatures are falling to their equilibrium values, indicating that they are seeing space as we expect. We hope to complete the scientific activation of the XRT over the weekend, when we open the XRT Focal Plane Camera Assembly door.
The Figure of Merit activation has continued, including a response to a BAT trigger caused by lowering the BAT thresholds to the point where random noise caused a trigger. The Swift ACS and spacecraft properly responded to the trigger request, and we are happy that the automated response system is working as we expected.
We continue to analyze the TEC Power Supply information, to see if we can activate the TEC. In parallel, we are considering options for the behavior of the CCD without the TEC cooling. At this point our in-orbit data shows that we can maintain the CCD temperature in the range of -55 to -60 C. In some spacecraft attitudes we have achieved temperatures as low as -70 C. This information, combined with the X-ray CCD spectra we are currently collecting, encourages us to predict that the XRT will perform as least as well as the ASCA SIS CCD experiment, and that we are currently performing as well as the CCDs in the ACIS experiment when the GTO phase commenced.
I am confident that we will fully achieve the goals of the XRT in measuring the position and flux from X-ray counterparts of newly discovered GRBs. Moreover the Swift XRT X-ray spectra will be measured with sufficient resolution to confirm and measure any substantial X-ray spectral features in GRBs.
Dec. 6, 2004
Swift had a good day today. The Figure of Merit process, (hosted within the BAT computer) was enabled and tested for the first time. This included loading an ATS (Automated Time Sequence) to the on-board computer, that was generated from a PPST (Pre-Planned Science Timeline) made by the MOC. These PPSTs will be the way Swift will be programmed to observe targets (such as older GRB afterglows) when no brand new GRB is visible. This testing went smoothly. Tomorrow we will make the first automated slews under FoM control.
The XRT team continued to investigate the TEC Power Supply. They telecon'ed with Southwest Research Institute to advance the investigation. XRT also reenabled the XRT tube heaters, continued camera venting, and collected data to optimize the bias levels for the current temperature.
Tomorrow we plan to open the XRT telescope door and do more FoM testing.
Dec. 5, 2004
Following the pre-launch plan, Swift operations are transitioning from the initial 14 days of 24/7 commanding (which required that the spacecraft, FOT, and Mission Directors support alternating 12 hour shifts), into a schedule with 12 hours of commanding staffing, alternating with 12 hours of on-site health monitoring. We will start tomorrow at 4 AM with the first 12 hour command shift.
The XRT team has been collecting data and is at work on creating a plan for activating the Thermo-Electric Cooler. Whether or not the TEC is activated Swift plans to implement and test the Figure of Merit (FoM) on-board software. The FoM is the key part of the ability of Swift to autonomously slew to new GRBs and ToOs. XRT plans to open the outer telescope door on Tuesday morning.
If the XRT is unable to activate the TEC, we have determined that the effect will be a warmer and less stable operating temperature for the CCD detector. The scientific impact would be that Swift would still reach its Level I requirements of positioning GRBs to 5 arcsec. Spectral resolution would slowly increase with time affecting secondary scientific objectives, but at modest (few % per year) rate and with performance near nominal for the first years. The instrument would require more substantial on-orbit calibration time and new CCD waveforms would need to be developed and tested to reduce the effect of higher thermal background and greater sensitivity to radiation damage effects.
Dec. 4, 2004
The XRT attempted to turn on the Thermo-Electric Cooler for the CCD X-ray detector. They were not able to succeed in turning on the TEC, due to a drop in the input voltage to the TEC power supply. The XRT team is investigating the reasons for the drop, and accumulating housekeeping data to develop a plan. The spacecraft collected more ACS slew data to calibrate the ACS with the current (planned to be final) parameters.
Dec. 3, 2004
The BAT team (lead by Scott Barthelmy, with processing performed by Derek Hullinger) made an image of the sky from BAT data from only 120 seconds of data, and only 1/4 of the full array. This image clearly detected the source Cyg X-1 at a 25 sigma confidence level. The PSF was in perfect agreement with pre-flight predictions, and using pre-flight alignment predictions agree with the known location of Cyg X-1 to within 8'. This is a great accomplishment, and we're all happy and proud of the BAT team's result.
The BAT activated four more detector blocks of CZT detectors (now 16, 384 out of 32,768 in the full array). The XRT has collected an image showing that the UV/optical blocking filter in front of the CCD is intact. The activation of all systems is moving ahead of schedule and we are replanning to move ahead some activation tasks next week. Tomorrow the BAT will start enabling two more blocks (4096 detectors). XRT also plans enable the CCD Thermo-Electric Cooler morning to collect operational temperature X-ray spectra from the door radioactive source. Figure of Merit testing will begin Monday morning.
Dec. 2, 2004
Swift continued with more progress in activating the instruments. The BAT activated two more detector blocks of CZT detectors (now 8192 out of 32,768 in the full array). These detectors show leakage, temperature of operation and counting rates that are similar to the first set. The XRT has enabled the operational heaters for the past two days, and the mechanical stability (as measured by the Telescope Alignment Monitor) is excellent (no variations above 1" across the full sun-eclipse orbital transition and across the full range of attitudes during operations). XRT is now collecting door closed background frames to characterize the effective extent of the SAA for the XRT CCD camera performance. UVOT continues routine monitoring and shows nominal behavior. The ACS team is very happy with the performance of gyros #1 and #3 and has selected them as the initial operating pair. The activation of all systems is moving ahead of schedule and we are replanning to move ahead some activation tasks next week. Tomorrow the BAT will start enabling two more blocks (4096 detectors). XRT plans enable the CCD Thermo-Electric Cooler on Saturday morning to collect operational temperature X-ray spectra from the door radioactive source.
Dec. 1, 2004
Swift continued with more progress in activating the instruments. The BAT activated the second detector block of CZT detectors (now 4096 out of 32,768 in the full array). These detectors show leakage, temperature of operation and counting rates that are similar to the first set. The XRT sees increased camera outgassing from the elevated camera temperature due to the operational heaters being on, and they collected a backward clocking CCD frame to measure camera readnoise. UVOT continues routine monitoring and shows nominal behavior. The ACS team feels they are nearing the completion of ACS tuning and are starting to load our initial set of operational parameters. They will then collect data about the ACS performance through Friday. Tomorrow the BAT will start enabling one or two blocks (either another 2048 or 4096 detectors). XRT hopes to enable the CCD Thermo-Electric Cooler on Saturday to collect operational temperature X-ray spectra from the door close radioactive source.