SPP/ FIELDS Modes and Operations

1. SPP/FIELDSModes and Operations Stuart D. Bale, Keith Goetz 18 July 2013

2. FIELDS Clocks • FIELDS instrument to use unified clocking • Receivers, sampling, power supplies, clocks • FIELDS HF instrument relies on picket-fence for RF sensitivity • Power supplies chop – making lines noise as a function of frequency • Un-avoidable but controllable chopping at controlled frequencies • All power supplies must be controlled • N * 50kHz with N starting at 3 – e.g. 150kHz, 200kHz and so on • Frequencies are crystal controlled (±100PPM) • Make observations as a function of frequency in between lines of noise • In earlier analog super-heterodyne receivers, we used sharp crystal filters to create the picket fence • Observing in between lines of noise

3. Picket Fences

4. FIELDS Clocks • In the past, we used sharp crystal filters to create the picket fence • With our new all-digital receiver, we implement sharp picket-fence filteringwith simple time series and poly-phase filtering • Samples must be in sync with FIELDS’ and S/C power supplies • FIELDS/HFR high end is about 20MHz – sampling at ~40MSa/s • Exact frequency must fall on the picket fence with room for an FFT • Master sampling frequency is thus of the form 150kHz * 2^N • Master sampling frequency is 150,000 * 256 Hz is 38,400,000Hz

5. FIELDS Clocks • Master clock is 38,400,000Hz (±4kHz) • Power supply chopping frequency is 150,000Hz • 38,400,000Hz / 256 • Other FIELDS instruments will be operated in synchronization with master clock and power supply chopping frequency (SWEAP too?) • For low frequencies we’ll shift down by powers of two to ~293 Sa/s • 150,000kHz / 512 (292.968750Sa/s) • However, making convenient and compressible packets still requires a packet size and cycle time corresponding to a power of 2 samples • A standard packet should start with 256 vectors • Giving a FIELDS internal cycle time of .87 seconds/cycle • 131,072 / 150,000 Hz • FIELDS’ New York second

6. FIELDS DC MAG • Two DC MAGs – in-board and out-board • Designed and built at GSFC • Two units are to be identical • Identical drive frequencies • Identical range and resolution – 3 ranges up to ±64knT • Identical AC heater frequencies (150kHz) • Identical sampling rates: ~293 Sa/s or 292.96875 Sa/s or 150,000/512 Sa/s • Sync’ed to overall FIELDS master clock • Sync’ed to SWEAP clock? • Common hardware interfaces to FIELDS’ DCB and TDS • Common flight software modes • MAGs produce chunks/packets at 256 vectors per cycle • MAGs produce samples at ~293 vectors per second • Out-board MAG survey data down-sampled by 8 to ~36.3 vectors/second • In-board MAG survey data down-sampled by 128 to ~2.3 vectors/second

7. FIELDS DC MAG • MAGs produce samples at ~293 vectors per second • Out-board MAG survey data down-sampled at ~36.3 vectors/second • In-board MAG survey data down-sampled at ~2.3 vectors/second • MAG telemetry chunks/messages/packets • Continuous B(t) - edge to edge • .87 seconds/cycle (131,072/150,000Hz ) • Powers of 2 vectors in length – nominally 256 vectors/packet • Powers of 2 cycles (.87s) in length • Ranges from • 256 vectors at 293Sa/s covering .87s and 1 cycle in duration – highest resolution • 256 vectors at 36.3Sa/s covering 7s and 8 cycles in duration – out-board nominal • 256 vectors at 2.3Sa/s covering 111s and 128 cycles in duration – in-board nominal • 256 vectors at 1.2Sa/s covering 222s in 256 cycles in duration – lowest resolution • MAG range/gain changes • Allowed between cycles (256 vector samples or .87s)

8. FIELDS AC SCM • AC Search-Coil Magnetometers (SCM) • Designed and built at Orleans • 3 Low Frequency axes - 1 Mid Frequency axis • FIELDS DFB – can sample all 4 SCM axes and all 5 electric axes • Sampled at 150,000Sa/s • Down sampled in powers of two • Lowest rate is ~293 Sa/s or 292.96875 Sa/s or 150,000/512 Sa/s • SCM telemetry chunks – continuous time series - edge to edge • Nominally 2 V(t), 3 E(t) and 3 B(t) • .87 seconds/cycle (131,072/150,000Hz ) • Powers of 2 samples in length • Powers of 2 cycles (.87s) in length • Low frequency DFB packets • 256 vectors at 293Sa/s covering .87s and 1 cycle in duration – lowest resolution • DFB samples in sync with DC MAGs

9. FIELDS AC SCM • DFB can sample from all 4 SCM axes and all 5 electric axes • Sampled at 150,000Sa/s • DFB low-frequency spectra • 4 spectra – 2 cross spectra - 112 log-spaced channels up to 9.4kHz • 1 cycle – .87s per spectrum – continuous coverage • DFB mid-frequency spectra • 4 spectra – 2 cross spectra – 112 log-spaced channels up to 75kHz • 60 cycles – 52s per spectrum continuous coverage • DFB mid-frequency select time series • Nominally 3 E(t) and 3 AC B(t) • Sampled at 150,000Sa/s • Burst triggered based on programmable quality • Recorded at 1% duty cycle in FIELDS’ internal memory throughout perihelion • Later selected and sent to telemetry by command

10. FIELDS AC SCM • TDS – 1 SCM axis • Time series triggered bursts sampled at ~2MSa/s • Burst snapshots simultaneous with V, E and SWEAP counts • RFS – 1 SCM axis • Sampled at ~40MSa/s • Spectra downsampled to 1MHz (~2MSa/s)