data:data_analysis_manual
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data:data_analysis_manual [2023/11/10 09:19] Terje Fredvik [Data products] |
data:data_analysis_manual [2024/01/23 19:27] eric buchlin [Burn-in Effects] corrected files published in data release 4.0 |
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| ==== Burn-in Effects ==== | ==== Burn-in Effects ==== | ||
| - | The SPICE detectors have microchannel plates (MCPs). Over time, the sensitivity of MCPs decreases at the locations of strong emission lines. This effect is referred to as "burn-in" and results in a flat-top or "self-reversal" to the line profile. This has already been noticed for the C III 977 line. As of November 2023, internal level-2 files are corrected for burn-in for six lines (files planned to be part of release 4.0). The effects of burn-in continue to be monitored, particularly for weaker lines for which a correction is not currently available. | + | The SPICE detectors have microchannel plates (MCPs). Over time, the sensitivity of MCPs decreases at the locations of strong emission lines. This effect is referred to as "burn-in" and results in a flat-top or "self-reversal" to the line profile. This has already been noticed for the C III 977 line. From data release 4.0, level-2 files are corrected for burn-in for six lines. The effects of burn-in continue to be monitored, particularly for weaker lines for which a correction is not currently available. |
| The lines that are being corrected (as of 2023-11) are: N IV 76.5 nm, Ne VIII 77.0 nm, Ne VIII 78.0 nm, C III 97.7 nm, Lyman-beta 102.6 nm, and O VI 103.2 nm. | The lines that are being corrected (as of 2023-11) are: N IV 76.5 nm, Ne VIII 77.0 nm, Ne VIII 78.0 nm, C III 97.7 nm, Lyman-beta 102.6 nm, and O VI 103.2 nm. | ||
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| * ''EAR\_TDEL'': light travel time difference between Sun centre to Spacecraft and Sun centre to Earth (seconds) | * ''EAR\_TDEL'': light travel time difference between Sun centre to Spacecraft and Sun centre to Earth (seconds) | ||
| - | The full list of keywords is given in the [[https://spice.ias.u-psud.fr/spice-data/documents/SPICE-UIO-DPDD-0002-1.4-Data_Product_Description_Document.pdf|DPDD]] - search for "Solar ephemeris keywords". | + | The full list of keywords is given in the [[https://spice-wiki.ias.u-psud.fr/lib/exe/fetch.php/public:spice-uio-dpdd-0002-1.8-data_product_description_document_spicefits_.pdf|DPDD]] - search for "Solar ephemeris keywords". |
| Users should make sure to correct the SPICE observing times for EAR\_TDEL in order to compare with observations from Earth-orbiting spacecraft. This is especially important for highly-dynamic structures such as flares or CMEs. | Users should make sure to correct the SPICE observing times for EAR\_TDEL in order to compare with observations from Earth-orbiting spacecraft. This is especially important for highly-dynamic structures such as flares or CMEs. | ||
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| ==== Units and uncertainties ==== | ==== Units and uncertainties ==== | ||
| - | The data cube (returned by the SSW object method ''get\_window\_data'' or by the Python ''astropy'' or ''sunraster'' libraries) of the SPICE level-2 files contains spectral radiances in units of W/m²/s/sr/nm. The wavelength vector has units of nm. To convert a radiance in W/m²/s/sr to erg/cm²/s/sr, it is necessary to multiply by 1000. | + | The data cube (returned by the SSW object method ''get\_window\_data'' or by the Python ''astropy'' or ''sunraster'' libraries) of the SPICE level-2 files contains spectral radiances in units of W/m²/sr/nm. The wavelength vector has units of nm. To convert a radiance in W/m²/sr to erg/cm²/s/sr, it is necessary to multiply by 1000. |
| Uncertainties on the spectral radiances can be obtained with: | Uncertainties on the spectral radiances can be obtained with: | ||
data/data_analysis_manual.txt · Last modified: 2024/03/29 14:21 by eric buchlin
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