すばるの観測装置で取得されたデータは、全て観測装置から FITS フォーマットで出力される。これらの FITS データはハワイ島ヒロの山麓施設 (ハワイ観測所) でアーカイヴされ、将来公開される予定である。アーカイヴの検索項目は、基本的に全て FITS ヘッダに含まれていなければならない。また、いくつもの観測装置のデータを一括して検索できるようにするためにも、FITS キーワードは可能な限り観測装置間で共通化すべきである。データ解析に関しては、解析に必要なパラメータは FITS ヘッダから抽出される場合が多い。解析処理ソフトウェアの共通化による開発作業の省力化を図るためにも FITS キーワードの共通化が望まれる。
そこで、すばるでは以下の FITS ヘッダルールを定める。
COMMENT Subaru Device Dependent Header Block for FOCAS
撮像関連：IMAG
分光関連：SPEC
偏光撮像：IPOL
偏光分光：SPOL
'_' (アンダースコア) を 1 文字つけて、それ以降は何を書いても良いこととするが、その文字列についても、同じものを時期によって違う意味で使ってはならない。観測制御と解析の連携をとるために、OBS-MOD は山頂観測制御システムからステータスとして取得することを推奨する (抽象化コマンドを用いた観測時)。
OBJECT
FLAT
DOMEFLAT
DOMEFLAT_ON
DOMEFLAT_OFF
SKYFLAT
DARK
COMPARISON
BIAS
STANDARD
STANDARD_STAR
TEST
注: 各 COMMON キーワードがすばる FITS データで重要である事由の一覧表
| Keyword Name | Reason |
|---|---|
| AIRMASS | Roughly estimated one is convenient in archival search |
| BIN-FCT1 | The basic keyword for image features |
| BIN-FCT2 | The basic keyword for image features |
| BITPIX | The basic keyword for image features |
| BLANK | The basic keyword for image features |
| BSCALE | The basic keyword for image features |
| BUNIT | The basic keyword for image features |
| BZERO | The basic keyword for image features |
| CDELT1 | The basic keyword for image features |
| CDELT2 | The basic keyword for image features |
| CRPIX1 | The basic keyword for image features |
| CRPIX2 | The basic keyword for image features |
| CRVAR1 | The basic keyword for image features |
| CRVAR2 | The basic keyword for image features |
| CTYPE1 | The basic keyword for image features |
| CTYPE2 | The basic keyword for image features |
| CUNIT1 | The basic keyword for image features |
| CUNIT2 | The basic keyword for image features |
| DATASET(*) | Only needed to OBJECT type data. Needed by DASH. |
| DATA-TYP | Used as an key for archival search and essential for data analysis.(DASH etc) |
| DATE-OBS | The basic keyword for image features |
| DEC | The basic keyword for image features (origin of RA2000 & DEC2000) |
| DEC2000 | DEC may not be written in J2000.0. The key for archival search by coordinate. |
| DETECTOR | The basic keyword for image features |
| DET-TMP | The basic keyword for image features |
| DISPAXIS(S) | Convenient in spectrum plotting of raw data. |
| DISPERSR(S) | The basic keyword for image features |
| END | Essential for FITS data |
| EQUINOX | Essential for knowing RA and DEC epoch, and calculating RA2000 & DEC2000 |
| EXP-ID | For the grouping of data by simultaneous exposure. |
| EXPTIME | The basic keyword for image features |
| EXTEND | Essential for FITS data with ASCII Table Extension. |
| FOC-POS | The basic keyword for observation description |
| FOC-VAL | Needed by QDAS in focusing task. |
| FRAMEID | This is the unique key for archival system. |
| GAIN | The basic keyword for image features |
| HST | The basic keyword for observation description |
| INSTRUME | This is used in online data registration at Hilo. |
| LONGPOLE(I) | The basic keyword for image features |
| LST | The basic keyword for observation description |
| MJD | This is used in data search as a unique key for time. |
| NAXIS | Essential for FITS data |
| NAXIS1 | Essential for FITS data with 2-d image |
| NAXIS2 | Essential for FITS data with 2-d image |
| NAXIS3 | Essential for FITS data with 3-d image as those from MIRTOS |
| OBJECT | The basic keyword for observation description |
| OBS-ALOC | Can identify the control mode and where the instrument was. |
| OBSERVAT | The basic keyword for observation description |
| OBSERVER | The basic keyword for observation description |
| OBS-MOD | The key for selecting data in data search in archival system |
| PCnnnmmm(I) | Essential for setting control command to telescope (moving object onto the slit etc) |
| POLARIZn(P) | The basic keyword for observation description |
| PROP-ID | Essential for setting view parameter in archival system |
| RA | The basic keyword for observation description (origin of RA2000 & DEC2000) |
| RA2000 | RA may not be written in J2000.0. Key for archival search by coordinate. |
| RADECSYS | RA and DEC may not be written in FK5. |
| RET-ANGn(P) | Essential in data analysis of polarimetric data. |
| RETPLATn | The basic keyword for observation description |
| SIMPLE | Essential for FITS data |
| SLIT(S) | The basic keyword for observation description |
| SLTCPIX1(S) | Convenient in making plot of raw data spectrum |
| SLTCPIX2(S) | Convenient in making plot of raw data spectrum |
| SLT-LEN(S) | The basic keyword for observation description |
| SLT-PA(S) | The basic keyword for observation description |
| SLT-WID(S) | The basic keyword for observation description |
| TELESCOP | Essential for knowing the origin of data |
| TELFOCUS | Can be one of the key for identifying the causality of empty image. |
| TIMESYS | Essential for knowing time system used in the data |
| UT | The basic keyword for observation description |
| WAVELEN(S) | Convenient in making plot of raw data spectrum. |
| WAV-MAX(S) | Convenient in making plot of raw data spectrum. |
| WAV-MIN(S) | Convenient in making plot of raw data spectrum. |
| WCS-ORIG(I) | Used for identifying WCS is written by toolkit or not. |