r58 - 19 Mar 2014 - 15:03:42 - CraigStephensonYou are here: TWiki >  Public Web  > SpacecraftObservatoryWeb

Spacecraft and observatory web pages

General information

  • The Herschel spacecraft has a modular design. On the left, facing the "warm" side and on the right, facing the "cold" side of the spacecraft, the middle image names the major components.: herschel_sketch.gif

* Herschel Observers' Manual (HTML) and PDF (6.2 MB)

Pointing calibration and performance

The table below shows the recent SIAM update history (from OD299 onwards) showing the SIAM file used in up-link and the suggested down-link one. The SIAM matrices are a component of the auxiliary context inside the observation context.

OD range SIAM used in uplink SIAM used in pipeline Suggested reprocessing SIAM Comment
299 0122_0001 0122_0001 0341_0001 The temperature of the STR CCD was lowered to -10 degC to carry out the pointing calibration campaign at the new reference temperature. Raised again at the following DTCP
300-319 0122_0001 0122_0001 0122_0001 STR CCD reference temperature set back to +13 degC
320-329 0320_0001 0341_0001 0341_0001 STR CCD temperature lowered permanently to -10degC. The SIAM used in uplink was computed using incorrect offsets (reversed signs in both Y and Z offsets) resulting in target misalignment of some 10 arcsec. The use of a correct SIAM in downlink fixes the astrometry problems
330-339 0320_0002 0341_0001 0341_0001 New SIAM computed with correct Y, Z offsets
341-342 0341_0001 0341_0001 0341_0001 Some refinements based on pointing measurements carried out in OD330
343-353 0320_0002 0341_0001 0341_0001  
354-... 0341_0001 0341_0001 0341_0001  

  • NEW A quite complete summary of current and past pointing performances can be found here
  • NEW A technical note on the Absolute Pointing Error (the estimation of its 68th percentile from calibration observations): CAS_APE_calc_1p1.pdf

Spacecraft health monitoring

Spacecraft temperature tracking

  • The figure below shows the temperature evolution of the main mirror (M1), the Cyo Vacuum Vessel (CVV) and the Sun-Shade (SS) of the Herschel Spacecraft since OD 50 (2009-07-02) to OD 630 (2011-02-02) plus M1 and CVV comparison to OD 1445 (2013-04-29):

M1CVVsunshade_temp_OD40-660.png M1CVV_temp_OD50-1445.png

Radiation environment tracking

  • The radiation monitor on-board Herschel is called SREM for Standard Radiation Environment Monitor. SREM raw and calibrated data products are delivered with the Herschel observations as part of the auxiliary context, inside the observation context. The SREM units detect and count electrons, protons and cosmic rays with a coarse spectral resolution and 20◦ angular resolution. The measurements are based on silicon diodes polarized in reverse by a high voltage. The SREM consists of three detectors, D1, D2 and D3, mounted in two heads. One head consists of a single silicon diode (D3) and its main entrance window is covered with an aluminium plate of 0.7mm, defining a lower energy threshold of ~0.5MeV for electrons and ~10MeV for protons. The other head uses to silion diodes (D1/D2) arranged in a telescope configuration. The main entrance window is covered with an aluminum plate of 2mm providing a threshold of 1.5MeV for electrons and 20MeV for protons.

  • SREM calibrated 5-minutes-rebinned counts from the 30th of October 2009 to 29 April 2013, a second plot zooming on the large solar Flares on the 23rd Jan and on the 7th of March 2012, the largest ever in the history of the Herschel mission:

sremr_od0170-1445.png sremr_od0950-1445.png

-- MiguelSanchez - 29 Apr 2013

-- CraigStephenson - 11 Mar 2014

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pdfpdf CAS_APE_calc_1p1.pdf manage 411.4 K 19 Mar 2014 - 15:02 CraigStephenson Calculation of the 68th percentile of the APE
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